By using the experiment results of R. H. Stolen's, a polynomial formula of the SRS Stokes spectrum is got by sampling and digitized fitting. Based on the formula, the Raman gain and noise figure properties of multi-wavelength pumping broadband Raman amplifier are obtained with considering the inter-amplifying between multi pumps. After numerical analyze, the characteristic curves of Raman gain and noise figure of different fibers G652, G653, G655 and LEAF are got.