In order to explore the effect of gradation on the angle of repose of coarse grain soil, gradation parameters d_max,c_u and c_c are calculated for different graded soils, the angle of repose of each gradation soil material is tested by experiment, the influence of gradation parameters on the angle of repose is studied. The results show:with the increase of d max,c_u and c_c, the angle of repose increases. On the basis of this, a method of normalizing the angle of repose and gradation is proposed, the relationship between the angle of repose and the gradation parameters d_max,c_u and c_c is found. The rationality of the formula is verified by laboratory experiments.