In order to solve the problem of poor heat dissipation effect of a certain type of truck crane, the principle of its hydraulic system was studied. According to the heat generation and heat dissipation characteristics of the main components, the mathematical model of heat balance of the hydraulic system was established. Based on the software AMESim, a simulation model of the thermal hydraulic system of the truck crane in the no-load state of the engine was established, and the accuracy of the simulation model was verified by comparing the temperature of the radiator inlet and outlet. The pressure loss characteristics of four pumps under high speed no-load condition were analyzed. The results show that the energy loss of No. 2 pump is the largest, about 38%. The heat generated by the energy loss of the multi-way valve and the center rotating body is the main heat source of the hydraulic system. No. 3 pump and No. 4 pump return oil heat production are also large, but because the original design of the return oil is not cooled, resulting in a poor overall heat dissipation effect of the hydraulic system of the truck crane. By introducing the return oil of the rotary system and the control system into the radiator, the improved multi-way valve outlet temperature is reduced, and the outlet temperature of the oil tank is also significantly reduced, which improves the heat dissipation effect of the hydraulic system. The improvement is reasonable and effective, and provides guidance for improving the thermal management and control strategy of the hydraulic system of the truck crane in the future.