Abstract: Adhering to the main line of system construction is one of the "six major principles" put forward by the Third Plenary Session of the 20th Central Committee of the Communist Party of China on the basis of the profound summarization of the valuable experience of comprehensively deepening reform since the reform and opening up, especially in the new era. The idea of adhering to the system construction as the main line to further deepen the reform in an all-round way originates from the Marxist system theory, based on the development and changes of the world situation, national conditions and party conditions on the new journey, and is rooted in the fertile soil of excellent traditional Chinese culture. The core essence of adhering to the system construction as the main line to further deepen the reform comprehensively is mainly reflected in the party's overall leadership as the fundamental guarantee, the people-centered philosophy as the fundamental position, upholding fundamental principles and breaking new ground as the source of vitality, the rule of law as the important guarantee, and the systems thinking as the mindset. Adhering to the principle of system construction as the main line, clarifies the strategic orientation of further deepening the reform in the new journey, lays the institutional foundation for improving the efficiency of national governance, provides institutional guarantee for promoting social fairness and justice, and provides institutional momentum for high-quality economic development, which is conducive to promoting further deepening the reform in an all-round way and promoting Chinese modernization on the new journey.

Key words: comprehensively deepen reform, system construction, institutional advantages, system modernization, modernization of national governance