Abstract: Two methods of decreasing the weight of the heat radiator in the forced air cooling system of the airborne radar (increasing the space between fins and decreasing the height of the fins) are compared and analyzed with the thermal simulation software ICEPAK in this paper. The results show that with the same weight decreased, increasing the space between fins is more effective to control the temperature rise of the heat units; the two heat radiators connected in parallel in the air cooling system affect each other, that is, when the structure and dimension of one heat radiator change, the heat transfer capacity of the other heat radiator will be affected.