It is very important to evaluate the reflection of low energy ion from a surface of solid for understanding the interaction between plasma and the first wall in a fusion reactor. When ion energy is lower than 1 keV, the influence of the surface barrier of solids on ion reflection gradually becomes important. In the present paper, the influence of the surface barrier of soids on ion reflection has been evaluated by extending the bipartition model for light ion transport to the case of the boundary with a rectangular surface barrier. Our computational results have shown that surface barrier can remarkably reduce the ion reflection coefficient, when ion energy decreases down to less than 10 times surface potential energy of the solids.