Promoting the financial system to provide high-quality services for China's economic and social development is the key point of further deepening financial reform.Based on data of 281 prefecture level cities in China from 2004 to 2020,this study examines how financial depth affects the level of market integration.Research has found that financial depth can promote regional integration development,mainly through raising the level of local infrastructure construction and optimizing the efficiency of labor and capital allocation to achieve it.The generality of this conclusion is ensured through a series of robustness tests such as using provincial-level samples,selecting instrumental variables for estimation using two-stage least squares,and changing vari-able measurement methods.Based on theoretical analysis and empirical testing,it has also been found that the digital economy can optimize the market environment of the financial industry and improve bank service capabilities,which will strengthen the effects of financial depth on integration.Further heterogeneity analysis indicates that the central macro level development plan and regional financial regulatory level are conducive to enhancing the positive impact of banks on integration,while excessively high local government debt levels may limit the positive impact of financial depth.The article enriches relevant research on financial development and integration,and can provide some opinions and references for building a unified domestic market and deepening financial system reform.