A stator interturn short-circuit (ITSC) is a common motor fault, which endangers the entire power system. The ITSC fault disrupts the three-phase balance of the motor windings, resulting in a change in the voltage distribution. The leakage current of the motor is an important indicator for assessing the status of the motor, which is determined by the voltage and the equivalent impedance of the winding to ground. This article theoretically analyzes the change of the leakage current before and after the ITSC, identifying some characteristic frequency components of the leakage current that can be used to diagnose the ITSC fault. Besides, a numerical simulation model is built to calculate the voltage distribution of the winding-to-ground with and without ITSC. Finally, the experimental platform is conducted, and experiments are carried out to verify the above analysis. The experimental results demonstrate significant alterations in the characteristic values associated with slight ITSC, which are independent of the operating condition.