There are periodic changes of meshing teeth in electromechanical integrated toroidal drive. Considering time-varying meshing stiffness, dynamics model and the corresponding differential equation of parametric vibration system are established. According to the theory of Floquet, judgment factor expression of system stability is derived, and the influence laws of system stability to mechanical and electrical design parameters are given. Then, multi-frequency resonances are confirmed by the numerical integral method in parametric vibration system, i.e. natural frequency, meshing frequency and combination frequency resonances, and the corresponding frequency responses are given. The results show that except the excitation frequency, natural frequencies and combination frequencies between natural frequencies and meshing frequency exit in system resonances. The frequencies of the maximum amplitude are located in the natural frequencies, but external excitation frequency. System stabilities and forced responses can provide theoretical basis for designing of structure and mechanical and electrical parameters.