Abstract: As a light quality, small volume and long working time equipment, the airborne phased array antenna has the problems of heat concentration and high heat flux which would affect its service life and reliability. Therefore, the key to improve the performance of the antenna is the rational allocation of radiator. Taking a typical airborne phased array antenna as an example, by establishing a mathematical model between the thermal resistance of the radiator and the total heat of the high-power device, the key geometric parameters affecting the heat dissipation are obtained. The thermal simulation model is constructed by ANSYS Icepak, and the radiator under forced air cooling is designed and optimized with the minimum thermal resistance of the radiator as the optimization objective function. The simulation results show that the method has the advantages of lower computation and simple implementation, and can effectively decrease temperature. It has high engineering practical value for the rational configuration of the airborne phased array antenna radiator.