UWB pulse diffracted by a perfectly conducting wedge in both frequency domain and time domain is proposed in this paper. By introducing a numerical solution for the transition function, the diffraction coefficient is investigated by using UTD in the frequency band between 0 to 20GHz. A directly time domain analysis is also carried out by using TD-UTD. The frequency dependence of the diffraction coefficients for both vertical and horizontal polarization is linked with pulse distortion, which gives a perspective view of diffraction process for UWB pulse propagation within the indoor environment.