Abstract: FAMSAP is used to calculate the non--linear lateral transient response of PWR fuel assemblies toseismic or LOCA excitation. It is mainly composed of three subcodes: two of which are for physics cal-cuation and another one is for plotting purpose, FAMSAP = FAMREC + FAFRES + PLOT.FAMREC was developed by EG & G Idaho, Inc., to supply the US NRC. FAFRES and PLOT weredeveloped at CIAE, Beijing, China. In the report, the functions of the FAMSAP are described andsome results of dynamic analysis for Qinshan assemblies are given. Finally, several acceptance critiriafor fuel assembly during seismic or LOCA condition are suggested.