High temperature of the radiator group is harmful to the power system and hydraulic system. In order to improve the heat dissipation performance of the loader, the flow field characteristics of the cooling chamber are analyzed by simulation and heat balance test. Firstly, the mathematical model of heat flow is established. Secondly, the flow field in the cooling chamber under different speeds is simulated based on CFX. And then the influence of fan position and internal flow field distribution on radiator performance is studied. Through the simulation of four different distances, it is concluded that the optimal distance between cooling fan and radiator is 76mm. Finally, a testing system is built for the temperature acquisition of engine water radiator, torque converter oil radiator, hydraulic oil radiator and air-to-air cooler of the hood structure, and then the simulation results are verified. The test results show that the heat dissipation performance of the whole machine meets the requirements after optimization, and the optimized scheme can make the loader-digger in an efficient and energy-saving operation state.