As a major institutional arrangement for the construction of ecological civilization in the new era, central environmental protection inspectors are committed to strengthening the authority and responsibility of local government departments and guiding the environmental protection behavior of enterprises. The relationship between central environmental protection inspectors, local government competition and enterprises environmental protection investment is empirically studied by selecting Chinese A share listed enterprises from 2014 to 2020 as a research sample. The study finds that (1) compared to other types of firms, central environmental protection inspectors can effectively promote environmental protection investment in heavily polluted firms and form a certain sustained mechanism, but their effects continue to diminish as time advances. (2) When local government competition is low, central environmental protection inspectors can significantly increase the level of corporate environmental protection investment. (3) Non state enterprises and highly competitive enterprises are more affected by the central environmental protection inspectors, and the promotion effect of the central environmental protection inspectors in the “east central west” region shows a gradual weakening. In view of this, we propose to establish a long term mechanism of environmental protection inspectors, strengthen the responsibility of local environmental governance, standardize the competition order of local governments, optimize the assessment system of local governments, enhance the application of environmental protection inspection results, and efficiently implement environmental policies to promote the reform of ecological civilization system and improve the quality of ecological environment.