The third plenary session of the 20th CPC Central Committee pointed out that building a high-level socialist market economy system is an important guarantee for promoting the process of Chinese-style modernization. Based on this, this paper deeply discusses the connotation, characteristics, value implication and practice approach of the high-level socialist market economy system, aiming at responding to the spirit of the third plenary session of the 20th CPC Central Committee and promoting the process of Chinese-style modernization. This paper first reviews the formation and development history of the socialist market economy system, analyzes its theoretical connotation and practical evolution in different stages, and points out that the high-level socialist market economy system is an important achievement of the theoretical and practical innovation of socialism with Chinese characteristics. Then, the paper explains the basic connotation of the high-level socialist market economy system. High-level socialist market economy system not only puts forward higher requirements in terms of the relationship between the government and the market, state-owned economy and private economy, macro-control and national governance, but also emphasizes the harmonious coexistence of public ownership and various ownership economies, the organic combination of market mechanism and government role, and the key role of scientific and technological innovation and digital economy in promoting high-quality economic development. China will legally complete the upgrading of market system and market mechanism by building a national unified large market, promoting the market-oriented reform of factors, and improving the basic system of market economy. The paper also further discusses the value implication of building a high-level socialist market economy, and discusses the practical value of building a high-level socialist market economy from the dialectical relationship between productive forces and production relations, the contradictory movement of economic foundation and superstructure, and the internal relationship between national governance and development. It is pointed out that the production relations under the high-standard market system can provide institutional guarantee for the cultivation of new quality productivity, the optimization of superstructure can provide integrated efficiency for the development of economic foundation, and the modernization of national governance can provide driving force for social development. The importance of political system reform, improvement of legal system, and cultivation and innovation of talents in market mechanism construction enabling productivity development is especially emphasized. Finally, in terms of practical approach, the paper puts forward a series of strategies, such as giving full play to the effectiveness of government governance, establishing a healthy business environment, building a high-standard market system, building a modern innovation system, and building a unified national large market, so as to complement the effectiveness of the state-owned economy and the private economy, promote the optimization of economic structure, the modernization of state governance and macro-control to achieve the landing of a high-level socialist market economy system. This provides theoretical support and policy suggestions for China’s construction of a high-level socialist market economy in the new era, and is conducive to achieving sustained and healthy economic development and all-round social progress.