Digital inclusive finance is an important external force to promote the sustainable development of small and medium-sized enterprises(SMEs). In order to explore the role of digital inclusive finance on the sustainable development of SMEs, based on the 2014—2020 financial data of SMEs in the Growth Enterprise Market(GEM), this paper uses the Peking University digital inclusive finance index and SA index, and adopts the fixed effect and intermediary effect model. It empirically analyzes the influence process and mechanism of digital inclusive finance on the sustainable development of SMEs, and conducts robustness test by replacing dependent and independent variables. Finally, it explores the differences in effect of digital inclusive finance on SMEs among industries and regions, and conducts heterogeneity analysis. The results show that: firstly, digital inclusive finance plays a significant role in promoting the sustainable development of SMEs, more than 50% of which have been indirectly affected through easing financing constraints; secondly, through the heterogeneity analysis, it is found that the development of digital inclusive finance plays a stronger role in promoting enterprises, Internet and computer industry in western China. This paper provides enlightenment for the formulation and implementation of digital financial inclusion policies.