| The high risk geological hazard bearing body of anti dip layered rock slope exists universally in nature, In order to study the mechanism of instability and failure, In this paper, the anti dip slope rock is simplified to a cantilever beam with cracks, a fracture mechanics model of slope stability controlled by a set of structural planes is established, a method of the equivalent stress intensity factors for rock blocks and the relevant stability criteria are deduced. Secondly, the influence of 5 factors on slope stability is analyzed, including slope angle, thickness, length of structural plane, internal friction angle and cohesion. The results show that:①With the increase of the dip angle and the length of the structural plane, the unstable area of the slope increases, and the stability of the slope at the foot is smaller.②With the increase of internal friction angle and cohesion, the unstable area of the slope decreases, and the stability of the slope at the foot is greater.③With the increase of rock thickness, the scope of unstable rock strata is basically unchanged. However, as the thickness of the rock increases, the anti sliding stability of the strata will gradually move to the slope toe. The greater the thickness of the rock layer is, the greater the stability of the slope will be. Finally, The rationality and feasibility of the theory are verified through case studies. The research results have certain guiding significance for engineering practice.