Abstract: The spatial and temporal distribution characteristics of the future high proportion of renewable energy will present unprecedented challenges to the operation and planning of power systems.Owing to the radical change in the power system basic forms and operational characteristics,it is of great significance to study the transmission expansion planning considering high proportion of renewable energy planning.Based on former researches,four aspects of transmission expansion planning are introduced including the theory and method of coordinated grid-source planning,the transmission flexible planning method,the transmission planning coordinated with distribution network and the comprehensive evaluation and decision-making method of the transmission planning scheme.Finally,the key issues and prospects for future power systems with a high proportion of renewable energy are provided.