Abstract: The stability of surrounding rock in tunnels is a core scientific issue in underground mining engineering practices. In order to study the deformation and failure laws of surrounding rock in tunnels, this paper explores the action mechanisms of maximum principal stress, minimum principal stress, vertical plane stress, and maximum principal stress angle on the butterfly−shaped failure of tunnels, systematically reveals the mechanical evolution mechanism of butterfly−shaped failure of tunnels, and analyzes the deformation laws of surrounding rock under the influence of various changing factors based on the butterfly−shaped failure theory through numerical models. The results show that the size of butterfly blades in the butterfly−shaped plastic zone is positively correlated with the magnitude of stress applied. With the continuous increase of principal stress, compressive shear plastic zone exhibits significant convergence, and the distance between its geometric center and the tunnel boundary is negatively exponentially related to the principal stress, but with the plastic zone formed by tensile stress further expanding in the original direction. The impact of maximum principa stress on the displacement of surrounding rock is the greatest while that of minimum principal stress is the least. With the increase of maximum principal stress from 12 MPa to 50 MPa, the maximum displacement of surrounding rock increases from 0.098 m to 0.76 m, accompanied by a gradual increase in the displacement of left and right arch waists, arch crown, and arch bottom of the tunnel from the endpoints on both sides to the middle. The deviation of maximum principal stress azimuth triggers the counterclockwise rotation of the main extension axis of the plastic zone, without forming a complete butterfly blade. As plane stress is continually vertically applied, surrounding rock presents a self−organized equilibrium response, with a symmetrical equilibrium state formed between the compressive shear zone and tension fracture zone under the synergistic action of bidirectional stress. The shear stress at the junction of the arch crown and the two sides suddenly changes, and the left and right sides are respectively subjected to compressive stress and tensile stress.