Under the action of various natural forces, the disease of grotto temple is serious. With the passage of time, the damage degree of grotto temple is increasing, and the preventive protection problem of grotto temple is becoming more and more serious. The preventive protection of grotto temples mainly consists of numerical calculation and on-site monitoring. In order to ensure the accuracy of numerical calculation, this paper proposes the following research ideas: First, the three-dimensional laser scanning cloud image of the grottoes temple is used to generate a fine geometric model of the grottoes temple to accurately reflect the complex geometric shape of the grottoes temple; Secondly, H-B criterion is used to fully consider the deterioration of rock mass mechanical proper-ties caused by weathering, cracks, joints and other diseases, and obtain rock physical and mechanical parameter values close to the actual situation, and then establish a refined numerical calculation model that more truly reflects the boundary conditions, stress displacement and possible failure of the grotto. Finally, the existing stability of the grotto temple is analyzed by strength reduction method, and the danger area of the grotto after the deterioration of the rock mass is predicted by the longitudinal wave velocity of the rock mass, and an early warning system is established to realize the preventive protection of the grotto temple. Taking Grottoes No. 9 and 10 of Yungang Grottoes as an example, the above research ideas and methods are used to systematically model, force analysis and stability discussion. The results show the feasibility of this research approach, and can provide a reference for the preventive protection research of the grottoes with similar diseases.