Abstract: The process of fuel assembly dynamic analysis for accident condition was studied. Method of axial and lateral dynamic modeling was developed. The axial and lateral dynamic response calculation method was established, and then the grid impact force and guide thimble stress calculation were carried out. Based on ANSYS APDL and UIDL language, introducing the idea of parameterization and modularization, the fuel assembly dynamic analysis program (program-developed) for accident condition was developed. Compared validation was carried out using program-developed and software-specific respectively for a certain type of fuel assembly. Comparison results show that the difference was small, and in the range of engineering permissible error. The program developed can be used to analyze the fuel assembly accident instead of software-specific. Analysis ability of the program developed was stronger and calculation efficiency was higher than that of the specific software. Selecting a nuclear power plant as the analysis object, the program developed is used to do the dynamic calculation of fuel assembly for accident condition, and the analysis results meet the requirements of the code.