Large deformation and collapse may occur when irrational grouting pressure is used for reinforcement of tunnel surrounding rocks characterized by poor selfstability. In this paper, typical tunnel excavation crosssections are chosen, and a mathematic model in which seepage field and stress field are considered under various grouting pressures is established. The deformation of tunnel surrounding rocks under different grouting pressures is analyzed by means of multiphysical field coupling software COMSOL based on seepagestress coupling theory. The results of surrounding rocks Grade V show that: 1) The grouting pressure can be transmitted to surrounding rocks during grouting. 2) The stress field decreases with increasing length of grouting hole. 3) The stress significantly varies and passes to surrounding rocks. 4) The deformation speed of surrounding rocks rises rapidly in the primary phase and drops in later phase. In the end, the stability and safety of the surrounding rocks are guaranteed by using rational grouting pressure control technologies proposed in this paper, which can provide theoretical support and technical guidance for similar projects in the future.