Using the method of jet oil supplement, not only the problem of insufficient hydraulic pump oil absorption can be solved, but also overflow energy can be recycled from system. So the performance of the pump is improved, and the utilization of energy is increased. FLUENT software was used to simulate and calculate, the influence of the related parameters to the jet oil compensating device was studied and the best structural parameters of the jet device were obtained.So the device could have a larger ejector ratio.The research results show that using gradual shrinkage cavity, large pressure difference and small hole margin are helpful for the device to absorb oil.