Abstract: In the context of comprehensively deepening reform and high-quality economic development,state-owned enterprises (SOEs) and state capital have been endowed with new tasks and missions.In particular,the mixed ownership reform of SOEs is gradually heating up.One of the main objectives is to form a government mechanism featured with regulated shareholders’ behaviors,efficient and agile investment decisions and strong internal control by introducing a rich equity structure with non-public capital,reducing the proportion of state-owned equity and optimizing the corporate governance structure.Theoretically,the mixed ownership reform will inevitably affect the investment efficiency of SOEs.On the one hand,the dynamic change caused by its shareholding structure will exert a direct impact on its governance system and resource endowment,and it will harden the soft budget constraint on the SOEs,thus affect the investment efficiency of enterprises.On the other hand,the introduction of non-public capital through management shareholding and other ways can improve management incentives,improve equity diversity and balance degree,thus also affect the investment efficiency of SOEs.Then,there arises a question whether the mixed ownership reform of SOEs has practically improved the efficiency of enterprise investment.Empirical research on the listed SOEs from 2003 to 2017 shows that the mixed ownership reform has significantly improved the investment efficiency of SOEs,significant in restraining the excessive investment,while insignificant in the alleviation of the insufficient investment of SOEs.These findings may indicate that the mixed ownership reform improves the investment efficiency of SOEs mainly by reducing the excessive investment behavior and a more precise impact mechanism can be seen.SOEs bear more policy tasks,so they are more likely to engage in excessive investment behavior.However,other non-state shareholders introduced by the mixed ownership reform can change this situation.SOEs will fully adapt to the market competition mechanism,thereby optimize the investment behavior and improve its investment efficiency.Further research also finds that the mixed ownership reform of SOEs has a more significant effect on investment efficiency in industries of low competition level and regions of low marketization level.The research conclusions above mean that China needs to further expand and deepen the reform in the mixed ownership of SOEs,attach more importance to the reform in monopolistic industries and promote the reform according to the regional and industrial differences of marketization.

Key words: mixed ownership reform of State-owned Enterprises, investment efficiency, over investment, under investment