Abstract: This paper presents the ultra wide band(UWB) channel measurement method and a new calibration procedure in frequency domain. Based on the system transfer functions and the analysis of factors which decrease the measurement accuracy, the influences of the azimuthal of an UWB antenna on the waveform distortions are analyzed and discussed. The transfer functions between transmitting and receiving antennas over all the directions are measured in anechoic chamber by vector network analyzer within the frequency range of 0.5 GHz to 16 GHz. The calibration algorithm using the complex division and the weighted average is presented to eliminate the impact of measurement hardware such as antennas. This method is employed in the in-vehicle UWB channel measurement and modeling. The accurate small scale fading parameters can be obtained.