Abstract: Three-capacity water tank is an experimental device that can be used to study the control of liquid level, flow rate, temperature and other parameters. It has important practical application value in control theory teaching and scientific research. Its function is that it can be combined into various control loops to verify various control algorithms and to simulate the type of industrial field control. This paper models the three-capacity water tank and improves the traditional PID control algorithm and fuzzy control algorithm. The fuzzy immune adaptive PID controller was designed by MATLAB/Simulink. The second-order and third-order liquid level control models of the three-capacity water tank were established, and the simulation experiment was carried out. The control algorithm was tested and verified by the upper computer software. Experiments show that the stability and rapidity of the control system are significantly improved compared to ordinary PID control and fuzzy PID control.