This paper studies the Ultra High Voltage (UHV) power tower target interferometry in TerraSAR Spotlight (TSX-SL) mode SAR images. Based on the 3D point cloud data acquired by high-precision Lidar, the tower target geometric projection and scattering mechanism are analyzed. In the UHV tower cross area of the SAR interferometry, the coherence are stable and the phase are smooth and consistency. However, the accuracy of the tower elevation derived by the phase is not so accurate, which means the phase noise are little bit high. Theoretically, the special designed tower cross's scattering mechanism are dihedral reflection. The test results show that the 10cm thick ice on the tower cross surface damaged the dihedral reflection. The radar scattering signal intensity is decreased nearly 8dB in this condition. This paper testified that the variation of the radar scattering intensity on the tower cross can be used to quantitatively evaluate towers' icing state.