The heavy duty trucks have large engine power and drive continuously in mountainous area, so the heat dissipation of engine is very important. In the traditional cooling system with fixed transmission ratio fan, the cooling capacity is insufficient and the engine is easy to be over-heated when the engine is working in low speed and heavy load conditions. Owning to the bigger size of electric motor compared to the hydraulic motor, it is not suitably applied to the heavy duty trucks. Contrasted with the electric motor, the hydraulic drive cooling system is widely applied in heavy duty trucks due to smaller size, larger power, continuous speed modulation and flexible installation location. However, the low transmission efficiency of the pump-motor system results in high power consumption of the cooling system. In this paper, the mathematical and simulation model of hydraulic-driven fan cooling system is established for the specific engine. The study applies the digital PID controller of continuous system to control the fan. The control algorithm of anti-integral saturation is compared with the conventional method. The results show that during the time progress of 700s, the mean power consumption with anti-integral algorithm respectively reduce by an average of 40.8%, 35.1% and 29.2% in the target temperature of 363.15K, 364.15K, and 365.15K compared with the traditional control method. Moreover, the PID control with anti-integral algorithm can improve the temperature control accuracy and effectively avoid the excessive cooling.