Abstract: It is not a feasible approach for the seism analysis of the small-scale nuclear facility to calculate the seism response spectrum by geology perambulation, but the spectrum can be gotten by consulting the criterions such as the ground design response spectrum for nuclear power plant. It is very difficult to analysis the liquid sloshing using the liquid-solid coupling method, and the engineering calculation can be finished finally using the affixing mass method based on the rigid wall theory. The coupling method of plane to plane can be adopted to simulate the bolts connecting structure of the motherboards on the tall vessel supported by long legs if the results of the conventional coupling method of point to point are rather conservative.