A new planned city is in the south of Port Fouad - Governorate Port Said, Egypt. Its residential buildings will be constructed on a raft. The main soil stratification at the site is soft soil deposits. Generally, soft soil deposits have a weak bearing capacity and excessive settlement characteristics. Before beginning any construction activities, it is important to improve the current soft soil to avoid these problems. It was suggested to stabilize the soil of the new city with stone columns. Stone column has been known as a useful technique to improve weak soils. This paper presents a comprehensive numerical investigation on different parameters that affect the design of the suggested stone columns. Finite-element analyses have been performed using PLAXIS 3D V.20 software. The effective parameters studied are the ratio of the Length of stone columns to soft soil height L/H, the ratio of the diameter of stone columns to its length D/L, the distribution pattern, centroid spacing between stone columns, Cushion soil thickness, and Compression index of soft clay. The investigation recommends suitable cost-effective parameters for the design of stone column in the studied site. The best ratio of L/H is from 1to1.25, which reduce the soil settlement from 48.91%to58.91%. The best ratio of D/L is 0.166 which achieve the best reduction of settlement by58.91%. A triangular pattern distribution of stone columns is the best one because it gives the least soil settlement. Optimum spacing between the centroid of stone columns of 2.15D-2.5D reduce the soil settlement by 24%to21.4%.