Based on the wavelet method of moment (MOM),difference field scattering properties between slightly rough optical surface and redundant particles above are researched.The integral equations about slightly rough optical surface and redundant particles are presented from basic electric field integral equations.Impedance matrix,composite scattering field and difference scattering field are obtained.Bistatic radar cross section calculation formula of the composite scattering model is given.Bistatic radar cross section and difference bistatic radar cross section are analyzed between different material one/double redundant particles and slightly rough optical surface with different incident angle and numerical experiments are shown.The scattering contribution and difference field scattering angular distribution of the redundant particles or rough optical surface are provided.