Abstract: The waveguide-slot array antenna and the transmitter/receiver (T/R) module are assembled together in the 3mm wave-band radar seeker system，which results in an increase in the working temperature and may lead to performance degradation. The thermal-electronic integration design method is proposed to keep the optimal characteristics of antenna in different temperature. An antenna prototype is designed and fabricated in the typical working temperature. The measured results demonstrate the effectiveness and feasibility of the design method.