Under traditional financial pattern, financing restraints restrict the technical innovation input of small and medium.sized enterprises (SMEs), however, digital finance can ease the financing restraints of the enterprises and further boost the technical innovation of the SMEs. The analysis by using the data of listed companies of China’s SMEs and GEM from 2014 to 2018 shows that digital finance development is more conducive to the increase of the technical innovation input of SMEs than that of traditional finance development, but financing restraints have significantly partial mediating effect in the process of digital finance boosting the technical innovation of SMEs, as a result, the alleviation of financing restraints is the main path for digital finance to promote the technical innovation of SMEs. The technical innovation of the SMEs, SMEs of high.tech industry and non.state.owned SMEs, which are more strongly restricted by financing restraints under traditional finance pattern, is more significantly boosted by digital finance, which further reveal that the alleviation of financing restraints is the main path for digital finance to promote the technical innovation of SMEs. In the regions with better institutional environment and higher economic development level, the boosting effect of digital finance on the technical innovation of SMEs is bigger. In addition, the using depth of digital finance and digitalization degree positively affect the technical innovation input of SMEs but the influence of its covering scope is not significant, and the pure increase of the using quantity of digital finance can not effectively alleviate the financing restraints of SMEs. Therefore, China should actively promote high.quality development of digital finance, make efforts to alleviate and wipe out the financing restraints under traditional finance mode, improve institutional environment, boost high.quality development of the economy and sufficiently bring into fully play digital finance boosting the technical innovation.