A deeplyburied tunnel opening was modeled numerically using the strain softening model based on the composite MohrCoulomb criterion with tension cutoff failure, and an orthogonal numerical experiment was conducted. These things were done to reveal the relationship between plastic strain with softening deformation in highsitu stress for rock masses and the surrounding rock displacement. The degree of influence of these strain softening parameters on the surrounding rock horizontal displacement were obtained from the results and the quadratic surface relation between these parameters and the surrounding rock displacement was given. This method provided a theoretical basis for the stability analysis of deeplyburied tunnels and made reference to actual engineering.