Reactor temperature control is one of the main control objects in the production process of humic acid liquid fertilizer. Because of its time-varying, nonlinear and time-delay characteristics, the conventional control effect is not ideal. In order to improve the quality of humic acid liquid fertilizer, aiming at the problem of how to accurately control the temperature of reactor, the dynamic matrix () predictive control algorithm based on control was adopted to achieve good control effect. The simulation results show that compared with the traditional control, the control algorithm reduces the overshoot, shortens the adjustment time, and shows better control effect.