In the experiments of diffuse backscattering from highly scattering media,the symmetry of the polarized-light diffuse backscattering(PDB) patterns are influenced by the its geometrical error,which prevents the precise analysis.An image pre-processing method is proposed to reduce the noise of the pattern images and correct the geometrical error by means of the median filter and the theory of moments,respectively.The experimental results show that the image pre-processing can eliminate the pattern asymmetry caused by the geometrical error of the system.It improves the analysis accuracy for the PDB pattern and makes the real-time measurement possible.