Based on the perspective of “reverse mixed ownership reform” of private enterprises involving the introduction of state-owned capital, an emprical study has been carried out on the relationship between reverse mixed ownership reform and technological innovation in private enterprises by using the multi-period double difference method (DID) with a sample of private listed companies from 2008 to 2020. Research has found that reverse mixed ownership reform has a significant effect on the promotion of technological innovation in private enterprises, which conclusion still holds after a series of robustness tests. An mechanism analysis reveals that by alleviating financing constraints and improving corporate governance, reverse mixed ownership reform mainly enhances technological innovation in private enterprises. A heterogeneity analysis shows that the impact of reverse mixed ownership reform on technological innovation in private enterprises is more significant in non-eastern regions and enterprises with a higher degree of industry competition. Therefore, it is suggested that government departments should actively seek for an promotion of the development of reverse mixed ownership reform in private enterprises, and create a financing environment that facilitates innovation in private enterprises so as to further improve the corporate governance structure of private enterprises.