This paper combs through and investigates old age Hu Qiaomu’s contribution to the CPC’s significant political theory. Hu Qiaomu was in the philosophical social science centre of China, and the decision centre of the CPC’s significant political theory in his later years. The special position enabled him to contemplate and investigate the significant political theory from an overall viewpoint of China. Meanwhile, as an expert of the CPC’s history, an encyclopedia-like scholor, he could examine the CPC’s significant political theory from an academic viewpoint. Due to his qualification of mastering Marxism, profound knowledge base,special position and multiple capacity, he could investigate the CPC’s significant political theory both politically and thearetically. Via taking the Reform and Opening-Up of China as the background, via combing through old age Hu Qiaomu’s political and theoretical point of view, this paper sees segment of a whole of the developing and changing course of the CPC’s political theory, intends to contribute a little reference material to the deep investigation of the scientific system of socialist theory with Chinese characteristics.Basing on the facts, taking historicism as criterion and the old age Hu Qiaomu’s contribution to the CPC’s political theory as thebreakthrough point, this paper combs through and comments on old age Qiaomu’s new cognition of maintaining and developing Marxism and Mao Zedong Thought, which are the CPC’s guiding thoughts; on the new thinking of what is and how to construct Socialism; on the new enquiry of correcting the“Left”wrong deviation of the CPC in Socialist period; on humanitarianism and alienation; on the research and new cognition of the new studying history and the relationship between arts and politics; on the realistic and theoretical meaning of his new cognition. This paper affirms his theoretical achievements, however does not whitewash the defect and partial opinion.The following parts are the content of this paper.Chapter 1, Hu Qiaomu’s new cognition of the CPC’s guiding thoughts in his later years. The following words are his new cognition of persisting, developing Marxism. The paper expounds Hu Qiaomu’s understanding of persisting the nature of Marxism, which he emphasized from four aspects, they are: persisting the world outlook and methodology of Marxist dialectical and historical materialism, persisting socialism and realizing the goal of communism, persisting the proletarian theory of benefiting the proletariat and the people and persisting the Marxist theoretic quality of making progress with the deveolping practice; the paper interprets his new viewpoint on the production of China-style Marxism------ Mao Zedong Thought and Deng Xiaoping Theory, which expressed how Marxism combined with the revolution and construction practice of China; the paper combs through his new understanding of the relationship between inheritance and development, that is the relationship between Marxism, Mao Zedong Thought and Deng Xiaoping Theory, the last one is the principle and line in a new period; analyses his new cognition of the criterion of developing Marxism; summarizes his new conclusion of the CPC’s developing Marxism from twelve aspects; sets forth his new reflection on strengthening Marxist research in the new stage. The following is the new analysis of persisting and developing Mao Zedong Thought. This part sets forth Hu Qiaomu’s objective evaluation of Mao Zedong’s historical position and the new exposition of persisting Mao Zedong Thought in his later years, thouroughly combs his new proposition of rigorously distinguishing Mao Zedong Thought from Mao Zedong’s thought and the old age Mao Zedong’s error, redefines the connotation of Mao Zedong Thought; practically and realisrically judges his new understanding of the three basic points of the soul of Mao Zedong Thought, which are seeking truth from the reality, following the mass line and maintaining independence and keeping self-reliance; objectively introduces his new exposition of both persisting and developing Mao Zedong Thought; objectively assesses the theoretical and parctical value of his new understanding of the CPC’s guiding thought from national and international point of view.Chapter 2, Hu Qiaomu’s new investigation of socialist basic theory in his later years. This part sets forth Hu Qiaomu’s counter-reflection on national socialist concept of China before Reform and Opening- up in his later years; combs through his proposition that there is dual relationship between socialism and capitalism, and if the former needs to be constructed it must learn from the latter; summarizes his new understanding of the connotation of the socialism with Chinese characteristics; analyses his new cognition of communist goal that should be from near to far future; comments on Hu Qiaomu’s related new investigation practically and realisrically. Chapter 3, Hu Qiaomu’s new cognition of how to construct socialism in his later years. This chapter consists of three parts. Part one, on cocialist economic construction. This part combs through Hu Qiaomu’s systematic reflection on the faults of the national economic construction before Reform and Opening- up theoretically and practically; interprets his new proposition of socialist economic construction in a new stage. Part two, on socialist democratic construction. This part summarizes Hu Qiaomu’s view on socialist democracy from the aspects of its position, connotation, form of socialist democracy and coordination of several democratic relationships. Part three, on socialist cultural and ideological progress. This part analyses Hu Qiaomu’s new proposition of the position, connotation, the relationship with material civilization and the core of socialist cultural and ideological progress. Via the investigation of socialist economic, democratic and cultural, ideological construction, this part summarizes Hu Qiaomu’s socialist construction view in his later years, gives old age Hu Qiaomu’s new exploration of how to construct socialism, appraises the theoretical value and practical significance of Hu Qiaomu’s new understanding of founding and perfecting socialism with Chinese characteristics.Chapter 4, Hu Qiaomu’s new analysis of the CPC’s“Left”wrong deviation in his later years. This part summarizes Hu Qiaomu’s new proposition of the cause, nature, launching theory and the lesson of the Great Cultural Revolution; combs through old age Hu Qiaomu’s new understanding of a series of socialist problems such as the function of class struggle, existent range, appraisal standard and dealing with the two kinds of heterogeneity contradiction in socialist stage; interprets his new understanding in his later years that the CPC’s history should not be simplified as the history of line struggle, and the CPC’s history can be analyzed by two tendencies; summarizes his new exploration of the origion of the CPC’s“twenty years Left wrong deviation”; appraises the practical meaning of his new undersatanding that affects the realization of the CPC’s briging order out of wrongs theoretically.Chapter 5, Old age Hu Qiaomu’s research on other great theoretical problems. This part summarizes his new theoretical probe into humanitarianism and alienation; his new understanding of the relationship between arts and politics; his new proposition of the CPC’s studying history concept, and appraises the theoretical and practical meaning of his new ideas. The remaining part. This part appraises old age Hu Qiaomu’s investigation of the CPC’s great political and theoretical problems; gives an objective, practical and realistic deliberation to some point of his theoretical research that is open to question; and probes the reason of his glorious achievement in his later years.