An energy management strategy is proposed to save both the loss in the hybrid powered traction system and the capacitance of the electric double-layer capacitors (EDLCs). The authors aim at providing a method to design appropriate capacitance of EDLCs under the proposed energy management strategy. The energy versus power plain is proposed to be used for designing the appropriate capacitance of the EDLCs, considering the requirement for the power and the energy of the EDLCs, the traction performance, and the limit of the current due to dc/dc chopper for charging and discharging the EDLCs. The proposed methods are verified by numerical simulations, assuming different load cases such as a local train and an express train in a nonelectrified line. The results in this paper can be extended to designing a method on how to manage the energy and decide the capacitance of EDLCs for the general hybrid powered systems to drive motors with inertial loads.