A simplified theoretical model was introduced for predicting distribution characteristic of explosive residue in horizontal orignating from surface layer of charge because of border influence. With the theoretical model of spherical grain dynamics of sparse two-phase flow in single dimension， computing formulas of velocity′s attenuation and scattering distance were built for explosive residue grains in horizontal. Then， a simplified theoretical model on distribution of explosive residue was put forward on the basis of a spherical space with radius equalling to maximum horizontal scattering distance of explosive residue grains with certain diameter. With this model，the distribution characteristics in horizontal of explosive residue grains were theoretically analyzed under condition of explosion in air. Results show that there exists a maximum value of scattering distance in horizontal for explosive residue grains with certain diameter，and the density of mass distribution of explosive residue firstly increases with incraesing of distance to a maximum value and then decreases with inereasing of distance. Theoretical result basically matchs the phenomena of distribution of explosive residue in experiments.