Adjacency effect of the optical remote sensing could be regarded as the convolution of the atmospheric point spread function(PSF) and the surface-leaving radiance. By simulating the atmospheric PSF with backward Monte Carlo method and calculating the surface-leaving radiance with MODTRAN model, the at-sensor radiance was obtained. The adjacency effects for different target and background under different propagation conditions were simulated and analyzed. The results show that target and background reflectivity affect adjacency effect significantly and the percentage of the radiance caused by the adjacency effect in the total radiance increases with the increase of the background reflectivity. Adjacency effect for dark target under bright background is more obvious than that for bright target under dark background. Given imaging height and area, the higher the imaging space resolution, the stronger the adjacency effect is. Effect of the surface meteorological range on adjacency effect is of high importance. The larger the surface meteorological range, the bigger the sun zenith angle, the weaker the adjacency effect is. These results could provide the basis for modeling the optical remote sensing imaging system with high precision and exploring the correction algorithm of the adjacency effect.