The liquefaction resistance of the granular assemblies subjected to various K0 consolidation history was examined using DEM from both micro and macro mechanical viewpoints. The following results are obtained: (1) The over-consolidation effect on the increase of liquefaction resistance originates from the increase of the effective mean principal stress and strengthening of the fabric. (2) The amount of contact energy accumulated among inter-particles increases as the OCR increases, and the total potential energy can be regarded as an index representing the liquefaction resistance of granular assemblies. (3) The over-consolidation history is reset as a result of effective stress reduction by static unloading or cyclic shear loading. (4) Effective stress reduction caused by static/cyclic unloading diminishes the over-consolidation effect. (5) The smaller the particle size, the easier the particle rotates, implying that the easily rotated fine grain particles promote the shear deformation of whole assemblies.