In the design of aircraft structure, the static strength of the structure is the basis for the successful design of the aircraft structure. On the basis of meeting the performance indicators, it is the constant pursuit of aircraft structural engineers to achieve the goal optimization of structural lightweight. As the mechanical connection between aircraft structural parts, the accurate expression of its elastic-plastic stiffness under high load will affect the accuracy of the nonlinear simulation results of the structural bearing capacity. In this paper, the wing box section of an aircraft was taken as the research object. The nonlinear finite element simulation was carried out by using the commercial software ABAQUS. The fasteners in the aircraft box section model were expressed by FASTENER elements, and the stiffness curve of the fastener was taken into account. In the process of nonlinear calculation, the iterative convergence problem caused by the irrationality definition of the stiffness curve was studied, the optimization method of stiffness curve based on the midpoint deviation was obtained, and the complex nonlinear simulation analysis was finally completed. The simulation results achieve a good simulation of the experiment, and provide a basis for adding a large number of nonlinear fasteners to complex models automatically.