Abstract: The material and coating of space antenna structure affect not only the energy loss of the electromagnetic field of the antenna, but also the thermal radiation and thermal balance process. Based on the mechanism of electromagnetic field of the antenna system, the mechanism of heat generation in a horn antenna is analysed. A simulation model of the electromagnetic field-thermal multi-physical field coupling is established. The heat loss and heat balance process of the antenna system using different materials and different thermal control coatings are simulated and analysed. The results show that both the chromate coating and carbon fiber material as antenna conductors introduce large thermal loss, which leads to a long thermal balance process and a high work temperature (up to 265 ℃) in thermal vacuum environment. The antenna with aluminum alloy body gold-plated and supplemented with thermal control coating is recommended. Further simulation shows these thermal control methods lead to good results. The thermal equilibrium time is shortened to 20 min and the temperature is reduced to 115 ℃.