In order to solve the sealing reliability and selective design problems of the plungers and cylinder liners of oil-water separated plunger pump, a plunger sealing performance experimental device and the loading system were developed to simulate the actual operating conditions of the hydraulic plunger pump, and the dynamic balance design of the experimental device was carried out. The simulation model of the loading system for the experimental device was established, and then a reasonable loading method was determined through simulation and comparison. The loading test and stability test of the experimental device show that the operation of the experimental device is stable and reliable, and the volumetric efficiency is within a reasonable range.