As the constraints of the ecological environment become increasingly strict, how to balance between environmental protection and economic development has emerged as a crucial issue. Based on the panel data of 281 prefecture-level cities in China from 2003 to 2017, this paper considers the information disclosure policy (EIDP) as a quasi-natural experiment and evaluates the impact of EIDP on green innovation with the gradual difference-in-difference (DID) model. Furthermore, the influence mechanism and heterogeneity characteristics are analyzed. The result shows that: 1) The EIDP implemented in 2008 significantly improves the level of green innovation among Chinese cities; 2) The mechanism of the EIDP include optimizing the innovation environment, increasing innovation input and gathering innovative talents. 3) Heterogeneity analysis shows that, the impacts of EIDP on green innovation in low- and medium-level industrialized cities are greater than high-level industrialized cities, while effects on cities with low- and medium-level of economic development are much lower than those with high-level of economic development. This paper provides new evidence to the green innovation effect of informal environmental regulation and reexamines Porter Hypothesis in order to offer new references to optimize future environmental regulation policy.