Objective: The paper elaborates on the connotations of fair and moderate benefit guarantee, analyzes the great significance and challenges of achieving fair and moderate benefit guarantee in improving the social security system with Chinese characteristics, and proposes ideas and measures for improving the fair and moderate benefit guarantee mechanism. Methods: Based on the fundamental theories of social security system and combined with the development requirements of Chinese path to modernization, a systematic analysis was carried out under the overall framework of medical insurance system reform. Conclusion: Fairness and moderation are scientific choices in the benefit guarantee mechanism, and they are interrelated, with different connotations. Fair and moderate benefit guarantee is the feature of the medical insurance system in the new era, which is of great significance to promote the high-quality development of medical insurance, promote common prosperity, and realize Chinese path to modernization. Realizing fair and moderate benefit guarantee faces challenges such as changes in the external environment as well as imbalanced and insufficient development of medical insurance in practice. It is recommended to solidly promote the implementation of reform policies and improve the quality of benefit guarantee based on the current stage of economic and social development. When all necessary conditions are available, adjustment and balance on a larger scale should be explored.