A reactor core in a thorium molten salt reactoruses graphite as a moderator and reflector. The graphitecore is a multi-layered arrangement of graphite bricks thatare loosely connected to each other using a system of keysand dowels. Consequently, the graphite core is a type ofdiscrete stack structure with highly nonlinear dynamicbehavior. Hence, it is important to investigate the dynamiccharacteristics of the graphite core. In this study, a threedimensionalsingle-layer graphite core model, which is apart of the thorium molten salt reactor side reflectorstructure, was analyzed using the explicit method inABAQUS 2016 to study the core dynamic behavior whensubjected to different excitations. The design parameters,such as the diameter of the dowel, the gap between key and keyway and the bypass flow gap between two adjacent bricks, were also considered in this model. To reduce excessive demands on available computational resources considering the effect of molten salt, the spring–dashpot model was applied to model the interaction forces between the molten salt and graphite bricks. Numerical simulation results show that the effect of molten salt is a reduction in the peak maximal principal stress, and a larger gap between two bricks is beneficial to maintain the integrity of the graphite core under earthquake loading. The results obtained by the simulation can be used as a reference for future designs of a molten salt graphite core.