For improving the power density of a homopolar inductor alternator (HIA) in a capacitor charge power supply (CCPS), a novel excitation compensation (EC) method is proposed in this article, wherein a compensation winding is installed in the HIA for providing pulse excitation and increasing the charge power. First, high-power and high-energy density requirements of the CCPS in the pulsed power supply (PPS) are presented, and the power density problem of the HIA caused by its homopolar structure is discussed. Second, methods for improving the charge power in the CCPS are studied, and a good way is to provide strong excitation to increase the machine electromotive force (EMF) during the charge process, whose difficulties are also studied. Third, a novel excitation-compensated HIA (ECHIA) is introduced and the principle and the effect of different EC circuits are analyzed. In the end, simulation results of the same size ECHIA and a conventional HIA show that the novel EC method can indeed improve the charge power in the CCPS and help the HIA achieve higher power density.