Abstract: In this paper, a new airplane detection algorithm of polarimetric SAR image based on polarimetric cross entropy and Ya-maguchi decomposition is proposed. First of all, the similarity parameters are computed between each pixel of PolSAR im-age and three canonical scattering mechanisms which contain surface scattering mechanism, left-helix scattering mechanism and right-helix scattering mechanism. Further, construct polarimetric cross entropy based on the similarity parameters. Then, Yamaguchi decomposition is adopted to extract double-bounce scattering component power. At last, detection feature com-bining polarimetric cross entropy with double-bounce scattering component power is proposed, and the technology of threshold segmentation is used to achieve airplane detection. Multi-look fully PolSAR datasets acquired by U.S.UAVSAR systems and U.S.AIRSAR systems are used to test and verify the efficiency of the new algorithm. The experimental results show that the novel method can detect airplane effectively. Besides, the detection result’s false alarms are less.