This paper investigates the liquidity impact of fintech development on commercial banks with a sample of 18 Chinese commercial banks over the time interval from 2013 to 2022. This paper constructs a basic regression model, three models with the introduction of mediating variables, and a model for heterogeneity analysis. An empirical analysis in this paper begins by analyzing the overall trend of data by conducting a descriptive statistical analysis of the selected variables; in the second step, it is determined whether the selection of the variables is reasonable through the test of multiple covariance; in the third step, regression analysis is carried out on the data to determine the relationship between the variables; in the fourth step, it is determined through the mediation effect model whether FinTech will have an impact on the liquidity of commercial banks through the selected intermediary variable impact; subsequently, a heterogeneity analysis is conducted to determine whether there are differences in the nature of ownership and regions in the impact; finally, a robust-type test is conducted to determine whether the results of the regression analysis are credible. The results show that the liquidity risk of commercial banks is significantly reduced as fintech companies strengthen their interconnection with commercial banks. In addition, the net interest margin cannot be used as a mediating variable for FinTech to affect the liquidity of commercial banks, but the results of the empirical analyses of the non-interest income share present significant, i.e., there is a mediating effect. Finally, the heterogeneity analysis shows that the liquidity of urban commercial banks and joint-stock banks is more sensitive to the development of fintech, meanwhile, the liquidity of commercial banks in the southern region is more susceptible to the development of fintech. The article concludes with some recommendations to the Chinese government and relevant commercial banks regarding the promotion of FinTech development.