Environmental audit is regarded as a kind of voluntary regulation and an important tool for environmental certification. This paper aims to investigate the impact of environmental audit on innovation strategy of enterprise in the short and long term, separately. Samples and dataset are established by 437 listed companies in China and their business and environmental data from 2009 to 2020, respectively. To identify the innovation strategy accurately, the innovation strategy of enterprise is divided into technology introduction, independent innovation, and technology cooperation. Environmental audit is selected as a proxy variable of voluntary environmental regulation. The results show that environmental audit positively affects technology introduction, independent innovation, and technology cooperation. Further, the sample companies are divided into two groups according to pollution intensity, and it finds that high-pollution enterprises are more inclined to technology cooperation and technology introduction in the short term. For these enterprises, they will not continue to upgrade technology in the long term after meeting environmental requirements. For low-pollution enterprises, the positive effect of environmental audit on innovation strategy is sustained, no matter in the long or short term. Besides, low-pollution enterprises are more focused on technology introduction and technology cooperation in the long term.