Interturn short-circuit fault is a kind of initial failure of the permanent magnet synchronous motor (PMSM) and serious consequences may be caused if it is left undetected. In this letter, a simple fault indicator is defined as the sum of the absolute values of amplitude differences between the stator currents, where the amplitudes of fundamental components of the stator currents are calculated by the frequency-tracking algorithm. Then, an online interturn short-circuit fault detection method is proposed for the PMSM. The experimental results validate the effectiveness of the proposed method.