When pump working, an axial force will be generated, affecting reliability and life time of pump.Using computational fluid dynamics method, the performance parameters of the pump at different speeds were obtained. The calculation results were very close to test results. It was proved that the simulation mode and computational method are relatively reliable. On the pump, balance holes with different diameter were cut to reduce axial force. The results show that the balance hole can effectively reduce axial force, at the same time it has little effect on the other properties of pump. At last, for the balance hole the optimum diameter is 2 mm.