Abstract: Magnetic field modulated machines have attracted significant attention due to their high torque density. Benefiting from dual magnetic field modulation, dual- permanent-magnet-excited vernier (DPMEV) machines exhibit even higher torque density. However, the complex modulation relationships make harmonic contribution analysis challenging. This paper proposes an energy-based harmonic contribution calculation method to address this issue. First, finite element analysis is employed to evaluate a 5/12/19-pole pair DPMEV machine, revealing that certain stator-side permanent magnet-generated air-gap flux density harmonics negatively impact back-EMF. Using the proposed analytical method, an improved DPMEV machine structure is developed to enhance overall performance. By strategically adjusting harmonic phases, the novel design effectively utilizes previously detrimental air-gap flux density harmonics to improve torque density. Experimental results ultimately validate both the analytical calculations and finite element simulations, confirming the method's effectiveness.