The evolution of the principal contradiction facing Chinese society is the basic premise that deeply affects the work direction of the Party and the state, and is the fundamental problem related to the overall development of the cause of socialist modernization in our country. Since the Eighth National Congress of the CPC, the profound understanding of the major social contradictions and the profound understanding since its reform and opening-up are the historical basis, the principal social contradiction is the externalization and concrete performance of the basic social contradictions and the principal social contradiction determines the direction of social development. Since China’s reform and opening-up, the social productivity has been greatly improved and people’s material and cultural needs have been significantly satisfied. The contradiction between unbalanced and inadequate development and the people’s ever-growing needs for a better life is the principal contradiction facing Chinese society. To be completely clear about the basis of the transformation of the principal social contradiction in the new era is of great significance for the people to pursue a better life and build a moderately prosperous society in all aspects.