This paper uses the 2D+T method for hull optimization of double-stepped planing hulls at the early-stage design. The method is applied to investigate the impact of various step configurations on the performance of stepped planing hulls in calm water and waves. The 2D+T method utilizes pressure distributions along the hull length to calculate forces in calm water and incorporates momentum variation theory to mathematically simulate rigid body motions in waves. Previous studies have validated the accuracy of this method. The paper conducts a parametric study on a double-stepped hull, analyzing the effects of different step configurations on hydrodynamic performance in calm and rough water conditions. The results suggest that optimal location of front step is somewhere near the mid-section, and that of rear step is in the vicinity of the center of gravity for steps with identical heights. It is demonstrated that this configuration minimizes the added resistance and wave-induced motions. It is concluded that the 2D+T method can effectively assist designers in hull optimization of stepped planing hulls in the early-stage design. Further research is recommended to consider the effects of step shape in the hull optimization.