In view of the spatial electromagnetic structure of variable-cross-section helical stator in toroidal motor, this paper proposes an inductance calculation method based on equivalent motor models. Firstly, the spatial helical currents in worm inner stator are analyzed to obtain effective current components, and then, equivalent motor models are established for the planet rotor during its revolution and rotation, and the relationship between its revolutionary and rotational electrical angles is derived. The inductance of helical windings in inner stator is derived by the double-reaction theory, revealing the periodic variation pattern of inductance with respect to the position of the planet rotor as well as the validity of the inductance. Through voltage and torque equations of toroidal motor, voltage limit ellipse, electromagnetic torque variation pattern, and the maximum torque per ampere trajectory are obtained. The results show that the voltage limit ellipse presents a class elliptical shape under the influence of quadrature-axis magnetic circuit saturation effect, and the electromagnetic torque fluctuates periodically with the revolutionary electrical angle of planet rotor. Finally, the influence of electromagnetic parameters of toroidal motor on the electromagnetic torque is analyzed. This lays a foundation for the optimization of torque control strategies and the promotion of engineering applications of this motor.