Accelerating the planning and construction of a new energy system and building a new pattern of energy system development is crucial for ensuring national energy security and achieving green and low-carbon transformation in China. On the basis of reviewing the development course of China's energy system over the past ten years and grasping the current situation of the international energy field and the new goals of China's energy development, this study clarifies the implications of a new energy system that is "safe and efficient," "clean and low-carbon," "multi-dimensional and collaborative," and "intelligent and inclusive." It explores the new energy system from the aspects of total energy consumption and structural evolution, security guarantee of coal, increase in reserves and production of oil and gas, and cost reduction and efficiency improvement of non-fossil energy sources. Moreover, a development strategy of adhering to systematic thinking, innovation, and reforms is proposed, as well as the construction goals of the new energy system by 2035 and 2050. Furthermore, key measures for the construction of the new energy system are recommended, including (1) promoting the green and low-carbon transformation of the energy sector, (2) promoting the coordinated development of urban and rural energy systems, (3) building a multi-drive energy-supply system, (4) strengthening research on key core technologies, and (5) establishing a new energy-evaluation system. The study is expected to provide theoretical guidance and practical support for the construction of the new energy system.