Abstract: In this paper, the seismic analysis software of reactor structure is studied, a necessarry connect procedure and the loads combination and sensitivity analysis procedure are developed, and the commercially available software used in the seismic analysis, the imported software and the developed loads combination and sensitivity analysis procedure are combined to set up a software system. The modeling and analysis techniques used in 3D nonlinear seismic analysis of reactor structure are studied, and the necessity and feasibility of conducting the seismic analysis of reactor structure with 3D nonlinear timing method is explored. The reactor structure 3D nonlinear model is established, and the seismic analysis and calculation of reactor structure is conducted by the direct integral calculus method and using ANSYS software. The loads needed in the stress analysis assess and the acceleration timing required by CRDM seismic authenticate experiment are proposed.