Abstract: Building a modern environmental governance system is a key measure to solve China's ecological and environmental problems, maintain natural ecological security boundaries and achieve high-quality development. Based on the review literature, the connotation and construction content of China's socialist modern environmental governance system is defined, the China's socialist modern environmental governance index system built, the problems in the existing governance system are analyzed. Finally the corresponding measures are proposed. The study holds that China's socialist modern environmental governance system under the background of green and low-carbon development means that under the leadership of the Communist Party of China, guided by Xi Jinping's Ecological Civilization Thought, guaranteed by the rule of socialist system and law, based on advanced cultural concepts, modern information technology, the China's socialist modern environmental governance system for comprehensive protection of the ecological environment system and a system for sharing and co-governance is established by the means of the administrative, economic, legal, social and other means, under multiple governance bodies including the government, firms, society etc. China has a good foundation for building a modern socialist environmental governance system. However, the existing system still has problems such as lagging in the top-level design of the governance system reform, incomplete protection of laws, regulations and policies, excessively weak supervision and monitoring of the ecological environment and execution, insufficient participation of the enterprises and public, and low governance capabilities. During the "14th Five-Year Plan" period and in the future, in order to build China's socialist modern environmental governance system under the background of green and low-carbon development, we must adhere to the leadership of the Communist Party of China, comprehensively deepen the reform of environmental governance systems and mechanisms, strengthen the construction of laws, regulations and policies for green and low-carbon development and the environmental monitoring and supervision (environmental protection supervision), promote the green transformation of key areas and enterprises, continuously enrich the environmental governance index system, enhance the citizens' consciousness of ecological and environmental protection, and improve public participation capabilities.