In view of the fact that the current tunnel monitoring measurement method cannot measure the displacement caused by the early excavation disturbance of the tunnel and the displacement lost by the failure to install the monitoring equipment in time， the deformation of the surrounding rock of the tunnel cannot be accurately predicted. Based on the full displacement theory， this paper proposes a relatively accurate calculation method for the loss displacement， the advance displacement， and the full displacement of the surrounding rock during tunnel excavation. Through the regression analysis of field monitoring data and the simulation of tunnel excavation by FLAC3D finite difference software， the research results show that： in the whole process of tunnel excavation， the internal displacement curve of surrounding rock is S-shaped including three stages of initial growth， rapid growth， and stable convergence. The influence range of the spatial constraint effect of the tunnel face is roughly within the range of four times the hole diameter. In the numerical simulation， the ratio of advance displacement to full displacement is the advance displacement ratio of surrounding rock， and the calculation result is 0.3~0.4， which is consistent with the actual deformation law of surrounding rock in the engineering site. Therefore， the full displacement of the internal deformation of the surrounding rock obtained by the research is more in line with the actual situation of the site. The research conclusions can provide a theoretical basis and reference value for the calculation of the full displacement of the internal deformation of the surrounding rock during the subsequent tunnel excavation process and the setting of the reserved deformation.