From the angular spectrum theory of beam, we obtain a transmission model in the paraxial approximation which describes the spin Hall effect of light, and we use this model to analyze the cross-polarization characteristics in spin Hall effect of light. By analyzing the change of cross-polarization intensity and incident angles we find that the spin splitting in spin Hall effect of light becomes stronger when cross-polarization effect is stronger. In order to facilitate the experimental observation, we choose the incident angle near the Brewster angle where it's spin Hall effect of light is much more evident, and from where we observe a strong cross-polarization effect. If we increase the cross-polarization components and reduce the light of original polarization direction at the same time, the spin Hall effect of light can be greatly enhanced. This is a promising method to develop new optical devices based on spin Hall effect of light.