In order to rationally and dynamically design the reserved deformation for tunnel excavation in soft and weak rock and avoid overbreakinduced lining concrete increase and clearance interfering of primary support, the influence of each construction procedure of bench method on tunnel deformation is analyzed by numerical simulation and site monitoring, and the control standard for deformation of each construction procedure is determined based on deformation distribution principle. And then the corresponding early warning systems and engineering countermeasures are established according to stepped deformation control standards; the final deformation of primary support can be predicted by site monitoring data of each construction procedure. The application results of the abovementioned methods to Xiaoshan Tunnel constructed by bench method show that the primary support deformation is within reserved deformation, the reserved deformation of followed construction circle is dynamically designed, and the concrete amount for primary support has been reduced by 12.86%. The results can provide reference for reserved deformation designed of tunnel constructed by stepped method.