This article presents a study on the liquid level control system of a double-capacity water tank. Through the mechanism analysis method, the transfer function and incremental state equation mathematical model are established, and a differential method is used to discretize the incremental state equation without linear processing to avoid system errors and equation time series. The dynamic matrix control algorithm is applied to control the incremental state equation, and a Matlab script program is used to implement the control process. The simulation results show that the DMC algorithm can effectively control the double-capacity water tank system to meet the control requirements, which can have important reference value for the research and application of double-capacity water tanks and predictive control algorithms.