Abstract: Based on the potential energy action functional （1） for dynamic analysis of fluid-solid interaction problems, where some rotations in a com-pressible-inviscid fluid have been constrained by means of a penalty coefficient B, formulas （16）, （19）, （20） and （22） of a compatible finite element and the corresponding substructure-subdomain model are derived. A computer program - FSIAP has been developed. Some examples concerning earthquake response of a Dam-water system are calculated. The results drawn in Fig. 2-Fig. 7 and listed in Table 1 show that the displacement finite element method with the frequency shift technique and the substructure-subdomain technique described in the paper is appealing. for computing dynamic response of fluid-solid interaction systems and that with the same accuracy the mode synthesis method is much more economical than general finite element methods.