Automatic target detection is always difficult in complex background. The Wigner-Ville distribution has a good characteristic that the images can be represented in spatial/spatial-frequency domains. Through the pseudo Wigner-Ville distribution, the statistical property of Rényi entropy is studied. The change of Rényi entropy’s statistical property in natural images when the man-made objects appear is analysed. Then a novel method for generating saliency map based on pseudo Wigner-Ville distribution and Rényi entropy is proposed. Target detection is performed when the saliency map is segmented using a simple and convenient threshold method. Experimental results show the proposed method can detect the military vehicles from complex earth background effectively.