On the hypothesis that polar rod-like molecule is orientation distribution, dielectric constant of granular film on material surface was calculated by using orientation order parameters and considering the effect of local field on polar molecules with permanent dipole moment and interaction energy between molecules and material surface. The results show that dielectric constant of granular film depends on relative dielectric constant of substrate material and distance between molecules. It is aslo found that interaction energy between molecules and material surface is the only influencing factor if molecule area is close to critical area. However, interaction of local fields becomes a major influencing factor if there is great difference between molecular area and critical area.