This research introduces a novel approach to selecting and designing magnetic cores for DC power optimizers. Unlike traditional methodsthat depend on the Area Product (Ap) and involve extensive trial and error to achieve the final design, the proposed methodology utilizestwo essential parameters: the Core to Copper Loss Ratio (γ) and the Window Utilization Factor (ku) for the inductor design process. Theloss models of the inductor are formulated based on these variables, considering the impact of DC bias, a crucial factor that significantlyaffects the inductor in high magnetic field strength applications. To minimize the overall magnetic loss, the PSO algorithm is applied. Thesimulation results validate the effectiveness and rationality of the proposed magnetic models and optimization strategy. Therefore, this approachprovides an efficient and effective alternative to the traditional trial-and-error approach for designing and selecting magnetic cores for DCpower optimizers.