The equivalent static analysis is Bishop’ total stress analytical method
which is recommended by Chinese Specifications for Seismic Design of Hydraulic Structure. Because of thinking no influence of the pore water pressure of inter-slice in static and dynamic state
the calculating results tend to unsafe. It is applied at analysis of pore water pressure of inter-slice which are the static distribution of pore water pressure based on FEM of static seepage field and dynamic pore water pressure increment in the light of dynamic liquefaction FEM analysis. A modified effective analysis method of equivalent static analysis is suggested. The computing result is satisfied in the dynamic stability analysis of a tailings dam.