Abstract: All-solid-state transmitter has high power consumption and produces large quantity of heat. When the transmitter is installed with many components in a small cabin, the temperatures of components and cabin are not uniformly distributed and the cooling effect is poor. In this paper, after the total power consumption of power amplifier module is calculated, the air cooling approach that the radiators of power amplifier module and regulator power supply module are fixed side by side (up and down) with a common wind path and two pumps (left and right) extract air from the foreside to the rearward are adopted. The heat emitting parts such as microwave power tube of end level high power amplifier and regulator tube of switching power supply are designed to be directly embedded in aluminum radiator polished in milling flutes. After calculation checking, the thermal design is verified to be reasonable and has reference value for the system design of the structure of high density solid-state transmitter and for engineering practice.