Northwest China is rich in wind and solar resources, and accelerating the construction of wind and solar bases can inject a large amount of clean energy into the central region, which is conducive to achieving the goal of “double carbon”. Large-scale construction of new energy bases into the grid so that the new energy sending-end system generation side of the strong randomness and volatility, all kinds of flexibility needs to increase dramatically, there is an urgent need to study the new energy sending-end system planning methodology under the conditions of uncertainty. Considering the impact of the uncertainty of a high proportion of wind and solar resources on the new energy sending-end system, the short-term flexibility supply and demand characteristics of the new energy sending-end system were analyzed, and thermal power flexibility modification, demand response and hybrid energy storage systems were introduced to improve the system’s regulating capability, so as to propose a multi-objective stochastic planning method based on scenario analysis. A multi-objective stochastic planning method based on scenario analysis was proposed for the new energy sending-end system in Northwest China, which was solved by the non-dominated sorting genetic algorithm II and the commercial solver Gurobi. Through case analysis, it is verified that the planning results of this method can cope with the flexibility demand and transmission service demand under different new energy and load scenarios.