Abstract: Seismic analysis of was carried out for the plant of 5 MW Nuclear heating reactor in Tsinghua University in order to check its safety properties.Finite analysis model was established using SAP2000 pro-gram,and the effect of soil on the structure was simplified.The internal forces of structural elements under seismic condition were calculated by the linear elastic method,and the actual bearing capacities of the structural elements were calculated using the method in the standards.Then the internal forces and the bearing capacities were compared to evaluate the plant safety.The results show that the plant frame structure is relatively weak,and some framing members would be disabled and part of the structure would collapse in a strong earthquake.These weak components need to be reinforced.