Abstract: In order to deal with the consumption problem caused by the access of high proportion of renewable energy, the transmission planning theory based on multi-scenario technology, robust optimization technology and coordinated planning technology is proposed. The theory is composed of four different planning methods under different applicable conditions or in demand scenarios, i. e., multi-scenario based random planning method of transmission network, probability-driven based robust planning method of transmission network, coordinated network-source planning method considering multi-source complementarity and transmission network planning method coordinated with distribution network. It can improve renewable energy consumption from the perspective of transmission network planning on the premise of security and stability. On this basis, the future transmission network planning methods are prospected, and the possible research areas are proposed, including satisfying higher security and stability requirements, coordinating more extensive source-grid-load storage flexible interaction, promoting the application of big data and exploring the incentive space of electricity market mechanism. The corresponding research difficulties and feasible solutions are discussed.