On account of the fact that it is difficult for radars to detect coati ng stealth metal targets on the ground, a new methodology of adopting millimete r wave(MMW) alternating current radiometer is proposed in this paper, with the p urpose of detecting ground based coating stealth metal targets when their engines are in operation. Based on the description to the configuration and operation princi ple of radiometer, the mechanism and method of anti coating stealth through MM W radiometric detection is analyzed in detail, associating with the ra diometric characteristics of targets under different conditions. And at the same time, some corresponding theoretical results are outlined. Then a series of sim ulative detection experiments are carried out by means of the 3mm band total po w er alternating current radiometer that has been implemented here. Furthermore, t he experimental results are presented and they are in accord with the theoretica l ones.Finally it is indicated that the methodology illustrated in this pap er can effectively detect coating stealth ground based metal targets when their engines are running, and it provides a new route to the area of anti coating s tealth.