Abstract: The aperture synthesis microwave radiometer spatial resolution is restricted to the antenna array physical aperture, and the targets in an array beam range can not be distinguished, which limits its further development and application. Modern spatial spectrum estimation algorithm in the concept of array signal process can break through the airspace Fourier transform limitation and realize the superresolution estimation to the targets in an array beam witdth. Using array signal process algorithm to the radiant object passive detection, this paper present an object radiation brightness temperature inversion mode based on the array signal process theory. The simulation and experiment result show that the mode, compared to aperture synthesis algorithm， can take the super resolution estimation to radiant targets. Moreover, the effects of signal correlation and signal to noise ratio on the algorithm are studied.