Abstract—This paper concentrates on a control method for the prediction of variable speed pumps working in parallel to keep them running close to the best efficiency point (BEP). First, theoretical models of parallel variable-frequency hydraulic pump characteristics were established. Then, we proposed an optimized control method that could perform on-line decision-making for the operating number and switch point of hydraulic pumps based on calculation and comparison of pump efficiency through continually monitoring parameters of parallel hydraulic pumps. The proposed method was applied to a water cooling system designed for steady high magnetic field facility with four high-pressure pumps that used differential pressure set point control strategy. The actual application of the proposed method demonstrates its superior performance over the original method by saving considerable power consumption while achieving the same task of high-purity water cooling circulation. The method is universal and simple for on-line implementation, which is suitable for parallel pumps in a variable flow system.