Abstract: The contact problems between the plate and shell often exist in nuclear reactor structure.In order to develop appropriately the reactor structure dynamic finite element model,it is important to correctly stimulate the stiffness characteristics between contact pairs.This paper focuses on the numerical calculation methods and the selection of reasonable contact arithmetic and parameter by comparing with experimental data.The nonlinear contact stiffness between contact objects in reactor structure is studied,and the numerical calculation methods are consummated.The study results verify that it can represent experimental behaviors by adopting Augmented Lagrange Multiplier method and plane stress model to analyze the contact stiffness between the plate and shell.