In the new era, the transformation of principal social contradictions in China is a historical change related to the overall situation, which is significant theoretical innovation of the Communist Party of China and profoundly reveals the new features, new connotations and new changes of China’s basic national conditions, being of great significance to the economic and social development of our country. A solution to the new contradictions has become a new task, and is also the fundamental task of the construction of socialism with Chinese characteristics in the new era. At present, the people’s needs in China show the trend of complexity, diversification and multi-level cross coexistence, and " unbalanced and inadequate development” has become the principal factor hindering the achievement of people’s yearning for a better life. Therefore, it has important theoretical and practical significance to reorganize the transformation of principal social contradictions since the founding of China, and clarify the social transformation and internal logic of the principal contradictions in the new era, which is helpful for us to understand and grasp the scientific connotation of the conflict, and deepen the understanding of present basic national conditions, to further discriminate inner logical associations of " new contradictions-new problems-new tasks” in the new age, identify the focal point at this stage and the next development direction and work, and explore the real path to resolve the conflicts. In this paper, through the anatomy and unscrambling trial of unbalanced and inadequate development in our country, and connotation evolution of " good life”, we reveal the transformation logic of principal contradictions. Then based on the internal relationship of the conflicts and movement rules, we resolve contradictions and put forward the corresponding countermeasures and suggestions combining with the current reality. This paper points out that, under the background of completing the building of a moderately prosperous society in all respects, we are supposed to resolve social contradictions in two aspects in the new era. On the one hand, we should deepen the supply-side structural reform, optimize the economic structure, vigorously improve the quality and efficiency of development and supply, and make efforts to solve the problem of inadequate and unbalanced development; on the other hand, we should scientifically grasp the time connotation of " good life” and dynamic characteristics in the development, promote the overall construction of the " five in one”, and better meet the growing needs of people in many aspects and at multi levels. In practice, we should focus on promoting the change in contradictory forces between the two sides, turn " imbalance and inadequate development” into " more balanced and more adequate development” through economic, political, cultural, social and ecological development based on the full range of efforts, gradually resolve barriers to people’s increasing " good life needs”, and promote the all-round development of human beings and the overall progress of the society.