According to the feather of the many mine shafts extends to the deep, a new high lift head mammoth electric diving pump for drainage was developed. To study the unsteady characteristics that caused by interaction between the impeller and guide vanes, the sliding mesh technology and RNG k −ε Turbulence models was adopted to simulate the unsteady flow in the pump. The pressure distribution characteristics of the relevant section for the impeller, guide vane and return guide vane was obtained by calculation. The unsteady pressure fluctuation characteristic of each monitoring point was analyzed in the electric diving pump. The effective lift head by calculation fits the actual situation, which is greater than the measured lift head and has only 5% relative deviation.