Introducing private capital and employing mixed-ownership structure are effective means and inevitable choices to enhance the vitality, control and influence of state-owned economy. An effective corporate governance structure that matches the mixed-ownership reform of state-owned enterprises is the key to the success of the reform. This study suggests that the mixed-ownership reform and corporate governance practices under the Singapore Temasek mode provide China with important experience in separating government functions from enterprise management, the system of board of directors, highly independent market-oriented operation, open and diversified international employment and value-based motivation and assessment. The empirical study shows that a company's shareholding ratio of the top five shareholders, total compensation of board members, total compensation of senior officers, shareholding ratio of the board of directors, shareholding ratio of senior officers are positively related to corporate performance, while the degree of check-and-balance ownership structure, the separation of rights of chairman and general manager, and the proportion of independent directors are negatively related to corporate performance. In addition, there is a big difference in the relationship between corporate governance and corporate performance under different types of controllers.The mixed-ownership reform practice of Northern International Trust Co., Ltd. in Tianjin was analyzed as a case study. This paper presents reform suggestions on such aspects as improving the relationship between the Tianjin Municipal Government and the state-owned capital investment platform by the mixed-ownership reform, the design of the corporate governance mechanism of the state-owned capital investment platform, and the design of corporate governance of participating and holding enterprises of state-owned capital investment platform based on the case study and the experience and theoretical results of the Singapore Temasek mode.