In this paper,STAP(space time adaptive processing) for an airborne fire-control radar to detect slowly moving ground targets is discussed.The system of this kind is characterized by its forward looking antenna,short wavelength,high flight velocity and low PRF,which results in the highly ambiguous Doppler frequency of ground clutter and large Doppler bandwidth of mainbeam clutter.Conventional processing can not give good performance of detection.This paper is focused on the features of detection of slowly moving ground targets by use of the airborne fire-control radar,and the cascade processing and joint processing are compared.Finally,simulation results are included to validate the conclusions.