In a three-dimensional ocean model with curvilinear coordinates horizontally and σ coordinate vertically, the adapted grids at σ layer for interpolation in the Eulerian-Lagrangian Method (ELM) is unreasonable over steep topography, because the vertical distance between the adjacent grids in the same σ layer is too large. So this paper proposed that the interpolation is taken in absolute vertical coordinates to improve ELM. Compared with the original ELM, the numerical experiments show that the improved ELM has lower numerical dissipation, higher accuracy, and better performance over steep topography.