Common prosperity is an important feature of Chinese modernization, and expanding the middle-income group is an important part of promoting common prosperity. Based on the macro and micro level data, it is found that the scale and proportion of middle-income groups in China continue to increase from 2010 to 2022, the income distribution structure is constantly optimized, and the level of common prosperity is generally on the rise. However, the middle-income group has not yet become the absolute subject, and the problems of urban-rural structural differences, group decline risks and regional imbalances still exist. Steadily expanding the scale of middle-income groups is still an important direction for promoting common prosperity. Expanding middle-income groups can enhance the wealth creation power of common prosperity, consolidate the income foundation of common prosperity, strengthen the human capital support of common prosperity, and stabilize the social foundation of common prosperity, so as to implement the achievements of modernization development more widely and continuously among all the people. The international comparison shows that the expansion of middle-income groups has mainly formed three models : public service and coordinated distribution-oriented, market-driven and employment tax support, and development-oriented national co-ordination-oriented. They have their own characteristics in institutional arrangements and operating conditions, and are also restricted by factors such as fiscal capacity, market conditions, government coordination capacity, and development stage. Combined with China 's reality, we should focus on expanding the coverage of middle-income groups, enhancing the ability of residents to continue to increase their incomes, improving human capital and development capabilities, and improving family welfare and risk protection systems, so as to promote more residents to enter the middle-income range steadily, and promote common prosperity with the continuous expansion of middle-income groups.