Liquid level as an important in the chemical industry and many other industrial production parameters, the measurement and control effect directly affects the quality of the product, so the liquid level control plays an important role in the industrial production. Because the liquid level of liquid level control system has nonlinear, big lag, outlet valve port mathematical model is difficult to accurately set up wait for a characteristic, the conventional incremental PID algorithm is difficult to obtain satisfactory control effect. To solve above problems, this paper designed the control using PLC, controlled by fuzzy controller, the form for the closed loop control system, in order to implement the constant of the liquid level. Simulation experiments show that the fuzzy PID control level, the system be able to complete the various automatic and manual pump start, stop, and no impact to switch, and fault alarm, a smooth transition.