This article uses the “Green Credit Guidelines” issued in 2012 as a quasi-natural experiment, using the statistics of A-share listed companies from 2008 to 2017, using the PSM-DID model to examine the effect and mechanism of green credit policies on the investment efficiency of heavily polluting companies, and taking into consideration the heterogeneous influence of the financial ecological environment on the relationship between the two. The research indicates that, after the Green Credit Guidelines were promulgated, the investment efficiency of heavy-polluting companies has been slightly improved compared with non-heavy-polluting companies and that the impact is more obvious in regions with better financial ecological environment. The research conclusions confirm the beneficial effects of the Green Credit Guidelines policy on the prudent investment of companies that cause serious pollution to the environment and improve investment efficiency, a provision of empirical evidence for financial leverage to drive the green economy transformation.