Model ranges have important influence on calculation accuracy and efficiency in numerical simulation. According to the problem of numerical simulation of deep tunnel excavation, the model longitudinal range value is investigated with the finite difference software FLAC3D and the compound failure criterion. First, the general law of deformation of surrounding rock in longitudinal direction and the influence of unexcavated rock plug on the deformation of surrounding rock in deep tunnel excavation is analyzed. Further, the influence of the proximal and the remote boundary on the deformation of surrounding rock at monitoring section is yielded by the error analysis with the Least Square Method, to present the suggestions of the model longitudinal range. The results show that when the distance between the tunnel front and the monitoring section is more than 10 times tunnel diameter, the constraint of unexcavated rock plug on the deformation of surrounding rock can be ignored. The remote boundary distance, as well as the proximal boundary distance, has a power function relationship with the maximum numerical error of the displacement. Moreover, the remote boundary distance has greater influence on the numerical error of the deformation than the proximal boundary. When the longitudinal range of model is not less than 7.5 times tunnel diameter for the deep tunnel excavation simulations, the accuracy of general numerical simulation will be satisfied.