In this paper, a method for evaluating the influence of noise on ultra-wide Bandwidth (UWB) based poles extraction is proposed. Three groups of tumors are chosen as the samples. Each group contains three tumor subcases with varying permittivities, conductivities or radii. White Gaussian noises with signal-to-noise ratios (SNRs) range from 25 dB to 50 dB are added with the tumor signals of each group. The Prony's method is used to extract tumor poles before and after noise additions. 1000 times Monte-Carlo experiment is conducted on each group. The results show that the Prony's poles extraction method has a good performance when SNR is higher than 25 dB in all three experiment groups.