Abstract: The research on the radar cross section(RCS) statistical characteristics is the foundation for radar image, target recognition and detection. On basis of the fully polarimetric radar experimental data of fixed-wing unmanned aerial vehicles(UAV) in Ku band, this paper analyzed the mean, variance and other statistical characteristics of UAV RCS at HH, VH, HV and VV polarization with different frequencies and directions. The research reveals that the RCS mean value of fixed-wing UAV in the co-polarization mode is 9 dBsm greater than that in the cross-polarization mode. In order to describe qualitatively the statistical distribution of the RCS fluctuation characteristics, we selected the frequency in 12 GHz and 14 GHz, took the maximum likelihood estimator as the initial value, and fine-tuned the parameters by using the nonlinear least squares criterion to achieve distribution characteristics fitting of UAV RCS with different polarization mode in Ku band. The results show that the Gamma distribution can describe preferably the statistical distribution of the UAV RCS at the co-polarization mode, and the Weibull distribution can fit well the RCS statistical distribution of the UAV at the cross-polarization mode.