Abstract: In order to study the influence of weak intercalated layer and its own characteristics on the stability of slope, the process of crack growth and the first principal stress evolution of the slope in the south slope of an open pit coal mine in Inner Mongolia under 4 conditions of different interlayer buried depth, dip angle of interlayer, thickness of the interlayer and the dip angle of the slope is studied by using tensile failure finite element model based on the theory of tensile failure. The results show that the cracks in the slope are more likely to link with the weak interlayer with the increase of dip angle of interlayer, the thickness of interlayer and the slope angle. Although the slope surface layer is more likely to break with the increase of the depth of interlayer, but the crack growth degree and interlayer depth present opposite law.