Abstract: In order to solve the problems of high energy consumption and low efficiency of mine drainage system, the optimization design of mine cascade drainage system is carried out based on particle swarm optimization (PSO) algorithm. According to the cascade operation theory of two different types of centrifugal pumps and the proportional law of speed regulation by frequency conversion, the relationship between the flow and head of the main drainage pump and the speed of the booster pump is deduced. Taking the efficiency of drainage system as the optimization objective, the extreme value is optimized by PSO algorithm. Under the rated speed condition of the booster pump, taking the current, voltage and power factor of the main drainage pump motor and booster pump motor, as well as their outlet pressure and flow as the initial parameters, the theoretical extreme value of the total efficiency of the drainage system is obtained by limiting the number of iterations, and the optimal speed of the booster pump is determined. Its feasibility is verified by the speed regulation experiment by frequency conversion. The results show that the proposed method for determining the optimal speed of booster pump has high speed regulation accuracy, which can ensure that the drainage system operates in the high-efficiency working condition area, so as to achieve the purpose of energy saving and consumption reduction. This research is of great significance to improve the efficiency of mine drainage system and increase the safety and reliability of drainage facilities.