Abstract: Currently, the Southwest Power Grid is promoting the construction of a new power system. The southwest power grid has a large-scale integration of clean energy, mainly hydropower, which depends on the weather. The system operation is facing serious challenges due to the lack of reliable power supply and the frequent occurrence of extreme climate. Firstly, this paper introduces China's Southwest Power Grid and market operation pattern. Secondly, learning from the power supply issues in the Sichuan-Chongqing region of the Southwest Power Grid under the extreme drought, and high-temperature climate scenarios in the summer of 2022, and based on the perspectives of the regional power grid and the marketization, the paper summarizes the four shortcomings of current power supply scheme of Southwest Power Grid, namely limited warning levels, short supply cycle, limited supply space, and a single supply resource. Therefore, research methods and framework for the power supply of Southwest Power Grid are proposed based on the concept of "double-level, full-lifecycle, full-space, and full-resources" ("one-double three-full"). Thirdly, the power trading system for supply sufficiency in Southwest Power Grid under extreme climate scenarios is constructed: 1) proposing the concept and level determination method of power supply warning and response for regional power grids, and constructing a double-level power trading supply warning and response mechanism for "provincial power grid + regional power grid"; 2) proposing medium and long term interruptible power supply varieties and constructing a "medium and long term + spot + emergency" full-lifecycle power trading supply guarantee system; 3) proposing the concept of inter-regional and intra-provincial market power supply, designing spatiotemporal exchange transactions of large-scale hydropower and constructing a "inter-regional + inter-provincial + intra-provincial" full-space power trading system for supply sufficiency; 4) proposing provincial medium and long term peak-shaving power supply varieties in load side and constructing a "generation side + load side" full-resources power trading system for supply sufficiency. Finally, a practical case study of the above research results in the Southwest Power Grid is presented to verify the innovation and practicality of the work. Meanwhile, this paper also provides general new ideas for power supply in other regional power grids with a large-scale integration of clean energy.