<p>This article investigates the influence of magnetic field modulation harmonics on the torque and permanent magnet (PM) losses of permanent magnet vernier machine (PMVM). First, the modulation processes of the PM magnetic field, armature (AM) magnetic field, and load magnetic field of PMVM are analyzed, the principles of torque generation and PM losses are revealed, and the effects of various harmonics on torque and PM losses are explained. It has been demonstrated that the load magnetic field configuration is influenced by the amplitude and phase of the PM magneto-motive force, AM magneto-motive force, and the permeance function, which can lead to interference between the AM magnetic field and the PM magnetic field. Positive interference raises PM losses, while negative interference suppresses them. As a result, this article proposes a multi-degree-of-freedom modulator design method that enhances torque and reduces PM losses by exploiting optimal working harmonics. Compared with a conventional uniform split tooth, the proposed design results in a 32% torque increase and a 49% reduction in PM loss. A prototype was constructed and experimentally tested, confirming the correctness of the theoretical and finite element analysis results.</p>