Abstract: The fractures of the rock mass will further expand under the action of plant root splitting, and the fracture propagation will lead to a decrease in the strength of the rock mass, which in turn will affect the stability of the surrounding rock of the cave. The research background is the large ancient underground cavern group in Shepan Island, Sanmen County, Zhejiang Province. Based on the theory of fracture mechanics, the mechanism of root splitting of three different root types of main straight root, scattered root, and horizontal root was analyzed. Based on the stress intensity factor of crack tip in fractured rock mass, the critical expansion force formula of plant root was established. the influence of plant root type and fractured rock mass properties on the root splitting of the surrounding rock of the cave was studied. The results show that the main straight root is easier to damage the fractured rock mass than the scattered root, and the deformation value is relatively larger when the failure occurs. The sandstone is destroyed earlier than the tuff, and the deformation value of the sandstone is greater than that of the tuff. The numerical simulation results of the stress intensity factor are in good agreement with the theoretical calculation results, and the average error is small. The research results provide a theoretical basis for the stability assessment and protective measures of the surrounding rock of the cave and provide ideas for the numerical analysis of the influence of plant root splitting on the stability of the surrounding rock of the cave, which has important scientific significance and application value for the prevention and control of cave disasters.