Abstract: Based on the theory of Marxist political economics, this paper tries to interpret the adaptive adjustment and interactive promotion of the economic system by following the internal orientation of economic system—social core economic system, basic economic system and specific economic system (including micro, meso and macro), and embedding the external orientation of the whole system: productivity—production relations (economic basis) —superstructure. The theoretical analysis main line and framework of the " Bidirectional Changes”, which is implicit and continuous throughout the text, aims to grasp the endogenousness of the changes of China’s socialist economic system and the self-consistency of the stage transformation, so as to gain insight into the deeper structural changes of the economic system in new China and the clues of the historical changes and the direction of the general trend. Further, objective and rational understanding of the path, characteristics and performance of the new economic system in the past 70 years is of great and far-reaching historical and practical significance for us to have a more sober understanding of the historical orientation of socialism with Chinese characteristics in the new era, more consciously enhance the value recognition of the socialist economic system with Chinese characteristics, and more firmly adhere to the high confidence in the socialist economic system with Chinese characteristics.