Guanjiao tunnel is the longest railway tunnel in China. The waterrich section of the tunnel reaches 22.5 km long. Due to the serious water inflow, there is great difficulty in the construction of the tunnel. Proper water pumping equipment is selected for No. 5 inclined shaft of Guanjiao and automatic water pumping is realized. In the paper, the principle of the automatic water pumping based on PLC controller and soft starter is presented, and comparison and contrast is made between the automatic water pumping system and the conventional water pumping system. It is concluded that the automatic water pumping system is superior to the conventional water pumping system in terms of economical efficiency and reliability. The automatic water pumping system has been successfully used in the construction of Guanjiao tunnel, and the construction cost has been reduced.