The longitudinal displacement profile (LDP) of the surrounding rock is the foundation for the supporting design of underground caverns using the convergence confinement method. However, in the LDP curve calculation with general numerical simulation method, it is difficult to determine the converging displacement of surrounding rocks accurately because of the wave-shape development and variation of the curve. To solve this problem, studies were conducted based on the relationship between the excavation step size and the accuracy of the numerical calculation grid in this paper. And the effect of curve and converging displacement of surrounding rocks caused by excavation simulation method and setting of self-weight of rock mass were analyzed. The results showed that the excavation step size has a great effect on the shape of the longitudinal deformation curve of the surrounding rock. The inappropriate selection of the excavation step size may result in obvious wave-shapeed variation. The determination of the tunnel excavation step needs to be closely combined with the accuracy of the numerical calculation grid when solving the LDP curve. The simulation method of rock excavation has no effect on the shape of the LDP curve, but it has a great influence on the true convergence displacement of the surrounding rock. The self-weight of the rock has no obvious effect on the shape of the LDP curve and the final converging displacement of the surrounding rock. When solving the LDP curve of practical projects, it is recommended to use the same excavation step size as the mesh length, which has no effect on the LDP curve shape and the absolute value of convergence displacement of the surrounding rock. The results of this study can provide references for solving the longitudinal profile curve of surrounding rock in the design of underground cavity support.