Abstract:      Improving enterprise total factor productivity is undoubtedly an important focus for high-quality economic development. Taking the commercial system reform as a "quasi-natural" experiment, this paper matches the data of commercial system reform of 286 prefecture level cities in China with the database of China′s A-share listed enterprises from 2010 to 2018, and empirically analyzes the impact of commercial system reform on enterprise total factor productivity and channel mechanism by using multi period double difference model.First of all, through the study of domestic and foreign literature, we find that very few papers focus on the impact of commercial systems reform on enterprise total factor productivity from theoretical and empirical angles. Therefore, this paper takes the lead in introducing a new round of commercial system reform into the analysis framework of enterprise total factor productivity from both theoretical and empirical levels, and explores how the commercial system reform can promote enterprise total factor productivity. This is important to reveal relationship between systems and enterprise total factor productivity during economic reform, optimize business environment, and promote high-quality economic development. It is also the original intention of the paper.Secondly, a multi-phase difference-in-differences model was applied for empirical evaluation. The estimated coefficient of the reform is significantly positive in benchmark regression results. The reform helps enhance enterprise total factor productivity levels. Fortunately, the conclusion was still credible after multiple robustness tests of alleviating non-parallel tendency, changing the measurement method of enterprise total factor productivity, eliminating interference from the Belt and Road Initiative and placebo. Then we conduct mechanism tests and heterogeneity analyses.At the end of this paper, the research conclusions and policy suggestions are given. This study shows that the reform was conducive to enhancing enterprise total factor productivity levels. Fortunately, the conclusion was still credible after multiple robustness tests of alleviating non-parallel tendency, altering proxy variable of enterprise innovation, and eliminating interference from the Belt and Road Initiative and placebo. What had been shown from impact mechanism was that the reform aimed to enhance total factor productivity levels of enterprises by reducing institutional costs of enterprises. According to heterogeneity analysis, more benefits were acquired by small, medium and micro enterprises as well as enterprises with more financing constraints from the reform. Through the conclusion of the study, we will continue to deepen the reform of the commercial system, implement the time limited completion system according to law, effectively reduce the examination and approval time of enterprises, improve the efficiency of the government, reduce the institutional transaction costs of enterprises, optimize the business environment of enterprises, release the vitality of the system and improve the production performance of enterprises. Second, the promotion of commercial system reform should be closely combined with enterprise heterogeneity, implement classified policies and make accurate efforts. Continue to provide more superior, fair and just business and access environment for small and medium-sized micro enterprises, so that small and medium-sized micro enterprises can enter not only the door of the market, but also the small door of the industry, and obtain greater "dividends" from the reform of the commercial system. At the same time, we will further deepen the reform of financial enterprises, improve supporting measures such as financing support and fiscal and tax incentives, effectively reduce the burden on enterprises and promote total factor productivity.

Key words: commercial system reform, total factor productivity of enterprise, difference-in-differences model, institutional transaction cost