Photovoltaic water pump system was a kind of environmental and sustainable new energy water pump system. Because the output power of PV array was unstable and discontinuous, it was hard to realize the 24hour continuous and efficient running. So a PVgrid water pump system was put forward. When the output power of PV array was insufficient, the grid compensates for the power shortage automatically through the power compensation controller. For the characteristics of the existing system was singlestage circuit, the limitation of the existing power compensation controller scheme was analyzed. And a new design was proposed, in which the threephase grid was directly connected to the DC bus after rectifier circuit. According to the design, the corresponding simulation model was built in the MATLAB/Simulink to verified the design. Then the function and efficiency of the power compensation controller were tested in experiment. The results of the experiments verified the feasibility of the design.