Aiming at the problem of constant water level control of water tank level, the dynamic mathematical model of single tank is established by mechanism analysis method. The dynamic matrix control algorithm is a single tank liquid level predictive control algorithm. Taking the state equation of liquid level as the prediction model, a dynamic matrix controller is designed and implemented. At present, the constant water level control of water tank liquid level is realized. The simulation results show that the proposed dynamic matrix control algorithm for liquid level of single tank has fast response speed, short adjustment time, strong anti-interference ability and good control effect.