Polarization Orientation Angle (POA) estimation and compensation with P-band, L-band and C-band PolSAR data are investigated previously. In this paper, we focus on the POA estimation performance with X-band PolSAR data. We analyze the effect of SAR image resolutions, signal to noise ratio (SNR) and scattering characteristics on POA estimation. Through the processing results of the airborne PolSAR data and TerraSAR-X PolSAR data, we can see that the POA estimation can be successfully executed in the building areas and non-vegetation covered areas, which will facilitate the PolSAR and PolInSAR processing. However, POA estimation will fail in other areas except for the built-up regions when the SAR image resolutions are below 3 meters even the high SNR of X-band PolSAR data. We illustrate the conclusions by PolSAR data experiments.