The growth and development of smes in science and technology is an important micro foundation for the implementation of innovation-driven strategy. In recent years, the development of fintech has more and more far-reaching impact on the growth of technology enterprises. Based on the data of specialized and ultra-new "little giant" enterprises from 2016 to 2021, this paper constructs an interactive fixed-effect model to empirically analyze the impact of fintech development on the growth of small and medium-sized technology enterprises. The study found that fintech development can significantly promote the growth of specialized, innovative "little giant" companies. However, this influence relationship is restricted by certain conditions. Enterprises with good business environment in the region, large scale enterprises and private enterprises are more significantly promoted by the development of fintech in their growth ability. Mechanism analysis shows that easing corporate financing constraints, shortening IPO process and reducing trial and error costs are the internal mechanisms for fintech development to promote the growth of technology smes. From the perspective of fintech development, this conclusion enriches the relevant research on the growth ability of small and medium-sized technology enterprises.