With the rapid development of electronic information technology in recent years, millimeter waves have been increasingly applied to communication, imaging, electronic countermeasures, radar, and guidance systems. In response to the limitation that domestic Successive Detector Logarithmic Video Amplifiers (SDLVAs) have difficulty in continuous detection in the millimeter wave band, a detection circuit design scheme based on the down-conversion mode is proposed. By using an internal local oscillator to down-convert the 26~38 GHz RF signal to 3~15 GHz, and then using a domestic SDLVA chip to perform continuous detection logarithmic video amplification on 3~15 GHz, the product design and testing show that this millimeter wave broadband detection can achieve a sensitivity of -57 dBm and a large dynamic detection output of 37 dB in a wide temperature range of -55~+70 ℃. The product features full domestication and miniaturization, giving it a significant advantage in broadband millimeter wave detection.