It is a worldwide problem that financing is difficult and expensive for micro, small and medium-sized enterprises. Bank credit financing is an important source of external financing. However, the current low financing scale restricts its effective play in alleviating financing difficulties. Does the rapid development of fintech help solve this difficulty? This paper studies this problem with the sample of New Third Board enterprises from 2011 to 2020. The empirical findings are as follows: (1) Fintech can significantly improve the access to credit resources for SME, and this conclusion remains valid after considering the endogeneity and robustness tests. (2) Mechanism analysis shows that fintech can significantly promote the credit access of SME by reducing information asymmetry, improving commercial credit financing and intensifying banking competition. (3) Heterogeneity analysis shows that the promoting effect of fintech on credit access is more obvious in the period of monetary policy tightening, regions with poor credit environment, central and western regions, high financing constraints, non-state-owned enterprises and enterprises with weak mortgage ability. (4) Further analysis shows that fintech can reduce borrowing costs; Compared with enterprises with short credit maturity structure, fintech has a more obvious positive impact on enterprises with long credit maturity structure. The research conclusions of this paper support the long tail effect and universality of fintech, and also provide an effective way for small, medium and micro enterprises to obtain credit resources and alleviate financing difficulties.