Abstract: In view of the research of the technology in millimeter wave passive detection coating-stealth targets, the mechanism of the characteristics of the coating-stealth targets with millimeter wave radiometer and the electromagnetic radiometric equation of the coating-stealth objective are analyzed, then the new general solution of the radiation transfer equation is given. The experiment of the double covered-stealth board with the 3 mm passive radiometer is given, the radiation characteristic distribution figure of the target is drawn with the experimental testing data, and which passive detection radiation properties and passive detection principle of the double stealth target board with millimeter wave seeker are analyzed.