Abstract: How to stimulate the vitality of state-owned enterprises and promote the high-quality development of China's economy is the current social concern. From the perspective of enterprise risk taking, this paper uses the data of A-share state-owned listed companies from 2003 to 2018, to investigate the relationship of mixed ownership reform, risk taking and innovation performance. The empirical results show that the mixed ownership reform has a significant positive correlation with the risk taking. The mechanism test found that the mixed ownership reform mainly affected the risk taking by reducing the agency cost of enterprises. Specifically, the effect of mixed ownership reform in improving risk taking is more significant in state-owned enterprises that have introduced private capital and those in regions with a high degree of marketization. Further research shows that the risk-taking level promoted by the mixed-ownership reform significantly increases the innovation input of enterprises but does not significantly promote the innovation output of enterprises. The results of this paper imply that in the process of mixed ownership reform of state-owned enterprises, a performance appraisal mechanism centered on innovation performance should be constructed to promote the formation of risk-taking preferences that are conducive to innovation activities and to promote high-quality development of state-owned enterprises.