The aim of this paper is to study the influence of the pollutants (oil spills) on the electromagnetic signature of sea surface observed in bistatic configuration. Therefore, we will start the numerical analyses of the pollutants influence on the sea surface roughness. Then, we will evaluate the electromagnetic scattering coefficients of the contaminated sea surface (sea surface covered by oil layer) in bistatic case by using the numerical Forward-Backward Method (FBM). The model used for the numerical simulation of bistatic scattering coefficients of clean and contaminated sea surface has been analyzed as a function of various parameters (sea state, type of pollutant, incidence and observation angles, radar frequency and polarizations).