Abstract: The analysis of the characters of interface between coal and rock in horizontal section fully mechanized caving mining of steep coal seam is conducted by using the loose stone particles. The different characters of interface between coal and rock under different rounds and different supports are got through the similar simulation. The characters are shown in mainly there aspects；the left and right interface between coal and rock appears after the top coal drawing and the right interface between coal and rock persistently keeps the shape that the slope decreases with level increases. The shape of left interface between coal and rock develops from the initial "mountain-like" shape to"π"shape. The permanent residual coal caused by coal-rock interface is mainly located in two positions, i.e. The lip shaped area near the floor and the "π" shaped area above the supports.