Abstract: This paper deals with the problem of adaptive detection on slowly-moving weak targets with airborne polarimetric radar in partially homogeneous clutter environment. The polarimetric adaptive Rao test is proposed with the Rao criterion and its performance is analyzed. The close-form s of probability of detection and false alarm are derived. It is proved that the Rao test ensures constant false alarm rate property with respect to the clutter covariance matrix and clutter power rate factor. Theoretical analysis and numerical experiments show that the polarimetric adaptive Rao test has better performance and lower computational complexity than the adaptive subspace detector and the adaptive matched detector, which are both designed with the generalized likelihood rate criterion.