As more and more offshore structures are built

seismic response of underwater site is gradually becoming a research hotspot.Based on arbitrary Largrange-Elurian description

this paper sets out governing equations of fluid motion in time dependent domain and point out contact condition between fluid and structure domain and controlling method of mesh motion in fluid domain.For even underwater site

according to Couette flow theory

this paper proves that fluid effect can be ignored under horizontal earthquake excitation;under vertical seismic excitation

horizontal uniform site can exactly consider fluid effect with dynamic pressure formula and horizontal non-uniform site need consider fluid effect with fluid-structure interaction method.Submarine tunnel is taken as an example to analyze this conclusion.For uneven site

dynamic response of natural types have distinct fluid-structure interaction feature under seismic excitation and a triangle prominence site is taken as an example.Dynamic response of manmade uneven underwater site caused by structure building also need consider fluid-structure interaction effect.And dynamic response of immersed tunnel under horizontal seismic excitation is taken as an example.Then simplified calculation method of fluid-structure interaction analysis of this type structure is set out according to result.