In Japan, a grid-form deep mixing wall method has been frequently used for many construction sites to prevent liquefaction. However, the effect of control on the amount of settlement and lateral displacement is still uncertain due to the effect of the variation of the distance between the walls, wall thickness and ground improvement by vertical and horizontal confinement. To understand the effectiveness of such configurations in liquefaction prevention, the different ground improvement cases of dynamic numerical analyses were performed using PLAXIS 2D software. As a new liquefaction mitigation technique, the effect of the grid-form with additional horizontal slab was introduced in this paper. In conclusion, based on numerical simulation results, it can be deduced that ground displacements are significantly influenced by wall spacing ratio, wall thickness and horizontal slab.