Abstract: As an important informal system, social trust is of great significance to economic and social development. This paper uses the panel data of listed companies from 2008 to 2014, to investigate the relationship between social trust and corporate innovation ability, and reveal whether social trust contributes to economic development. The result shows that social trust can significantly enhances corporate innovation ability, indicating that the informal system of social trust can affect economic development by promoting corporate innovation. Further research finds that the mechanism of social trust in promoting corporate innovation ability is that social trust can not only alleviate corporate financing constraints, but also make up for the shortcomings of formal systems. This study is of great significance for understanding the role of informal system such as social trust in promoting corporate innovation and even economic growth.