Abstract: Based on nonlinear vibration equations, this study employs the energy method to assemble beam element stiffness, mass, and damping matrices, thereby constructing an integrated computational model for the entire assembly. This algorithm was embedded into the ORCHID dynamic response analysis software, extending its capabilities to include seismic analysis of composite cladding fuel assemblies. Building upon this foundation, with zirconium alloy cladding fuel assemblies serving as a benchmark, the seismic performance of SiC composite cladding fuel assemblies was evaluated using the ORCHID software. The results demonstrate that the overall mass reduction of SiC composite cladding fuel assembly significantly alleviate the dynamic impact between the spacer grids and core baffle, thereby increasing the safety margin by at least 30%. Furthermore, the relative displacement and angular displacement between adjacent nodes of the guide thimbles are diminished during the peak seismic excitation. Consequently, both membrane stress and bending stress in the guide thimbles are reduced compared to zirconium alloy-clad assembly, the safety margins corresponding to the two stress criteria have been increased by approximately 1 and 6 times respectively. These improvements effectively mitigate the risk of exceeding stress criteria for guide thimbles during seismic events.