Abstract: The multi-unit machine is one type of the multi-three-phase machines, whose stator windings are composed of multiple three-phase units. Because multiple units of three-phase stator windings are distributed sequentially around the circle, the three-phase inductances within one unit are no more symmetrical. Taking a four-unit permanent magnet synchronous motor (PMSM) as an example, this paper pointed out that the asymmetry of inductances is due to the unequal mutual inductances, then explained why the asymmetric inductances may bring errors to the detection of the initial position of the rotor, and proposed an improved method to detect the rotor initial position considering the asymmetry of stator inductances. Based on the pulse voltage injection into stator windings, a modification method was proposed for the measured values of line inductance, which aims to eliminate the influence of inductances asymmetry on rotor position. The experimental results show that the proposed method can reduce the maximum detection error of the initial position from 12.4° to 3.2°, which effectively improves the detection precision of the rotor initial position for the multi-unit PMSM.