Abstract: Common prosperity is the essential requirement of socialism, and achieving common prosperity for all the people is the essential feature of Chinese modernization. The Multiple Streams Framework is appropriately used to systematically analyze the centennial changes of the common prosperity policy of the Communist Party of China (the Party). The study finds that the common prosperity policy of the Party can be approximately divided into four historical stages, that is the preliminary exploration, the tortuous development, advancing with the times, and the solid promotion. The shifts in the common prosperity policy of the Party at different stages are all the outcomes of the joint influence of the three streams, namely, the practical problems related to common prosperity that the Party faces, the Party’s political considerations regarding common prosperity, and the insights, recommendations, and policy measures concerning common prosperity from within the Party and from all sectors of society. In the new historical phase of common prosperity, we should optimize the formulation of the policy from four aspects, that is “problem streams”, “political streams”, “policy streams” and “policy windows”, which may have certain referential value.