Capital is the most basic element of production organization, and green bonds are important financing sources for the green industry. Financingcosts directly affect the steady development of the green industry. In order to verify whether third-party certification can reduce the financing cost of green bonds and whether the nature of property rights has an impact on the reduction, 285 green bonds issued from 2016 to 2019 are taken as samples, and then a hierarchical multiple statistical regression analysis method is adopted to conduct a quantitative study. The results show that third-party certification, as a unique credit enhancement method for green bonds, can significantly reduce green bond spreads. In addition, it isgreater that the effect on non-state-owned enterprises’ green bonds is. Since bond spread isamain part of financing costs, the above means that third-party certification can reduce the financing costs of green bonds, especiallyfor non-state-owned enterprises. In this regard, starting from reducing the cost of green bonds, the paper proposes to improve the green bond evaluation and certification standards as soon as possible, non-state-owned enterprises particularly should actively carry out third-party certification, and the government needs to further increase the implementation of third-party certification as well as strengthen multi-party cooperation.