The temperature of mash is an important parameter affecting the efficiency of ethanol fermentation. In order to ensure the efficiency of ethanol fermentation and improve the economic benefit of ethanol production. The Profit Loop control algorithm in Honeywell PKS system is used to design the mash temperature control system, and the model predictive control of the mash temperature is realized. After the system running test, the stable control of the mash temperature is realized. The execution frequency of the actuator is effectively reduced, the control effect is good, and the control requirements are satisfied.