Abstract: Hydropower is an important market body in the high-proportion hydropower market, which has an important and decisive influence on the clearing results. Due to the tight hydraulic spatial-temporal coupling relationship between cascade power stations and the clean absorption policy of hydropower, the spot clearing method is much more complex and difficult than the thermal power market. According to the characteristics of high-proportion hydropower market and the real demand of Yunnan power market, the daily power dynamic control of cascade hydropower stations was incorporated into the system constraint with the goal of minimizing the power purchase cost. Based on the iterative trading power, the linkage control boundary of the upstream and downstream was established, and the above objectives and constraints were automatically loaded into the optimization framework of the commercial solver, which was solved by the iterative optimization of mixed integer linear programming (MILP) model. Taking the actual daily power generation plan data of 122 hydropower stations and 11 thermal power stations in Yunnan power grid as reference, the simulation of the day-ahead spot bidding clearing was realized. The results show the hydropower spot clear plan can meet the cascade hydraulic constraints, and the calculation time is controlled within 3 minutes, which satisfies the timeliness and practicability requirements of day-ahead market clearing of high-proportion hydropower system.