In the construction and development of smart grid and energy internet, some key technologies should be given priorities to develop in different periods of time. Based on the concept of ideal power system and the development status of current power system, a systematic approach to analyze the development of key technologies of power system is put forward, and the development of the key technologies of the current power system is analyzed by using the proposed method. It is pointed out that the development priority of a technology not only depends on its contribution to improve the ideal degree of the power system, but also depends on the interaction between technologies and the economic benefits. At present, some technologies, such as big data, energy storage, new materials and cloud computing, should be given priorities to development.