Vacuum consolidation is a soil improvement technique that accelerates consolidation of soft ground by using the action of the atmospheric pressure in combination with a ground pore-pressure relief system. Dredged and reclaimed soft clays form slurry sta te which is very high water content and very low shear strength, experience large self-weight consolidation with nonlinear compressibility and permeability phenomenon. Applying vacuum consolidation method with horizontal drain in order to improve reclaimed soft ground, non-linear finite consolidation phenomenon takes place. To analyze the non-liner, finite consolidation of reclaimed ground, a material functions which represent nonlinear effective stress-void ratio-permeability relationship were obt ained with slurry consolidation apparatus and numerical analysis program was developed. From the back analysis of pilot test, a material functions which fit to field condition were obtained. It shows reasonably good match to the observed settlement. Design parameter’s effects with lateral vacuum method were analyzed.