An analytical method for calculating the incremental line inductance of a permanent-magnet synchronous motor is proposed in this paper. First, the incremental inductance is simplified as a linear combination of the slot inductance and the air-gap inductance, which are both estimated by the equivalent magnetic circuits. The reluctance of the rotor back irons and the stator back irons are ignored when the slot inductance is calculated. However, for the calculation of the air-gap inductance, the iron saturations and the perturbations of the permanent magnet are considered. The proposed method is verified by a finite-element method.