The incipient fault of a medium-voltage cable joint in a water-logged environment occurs before the permanent fault. Monitoring it can help prevent loss through the permanent fault. However, the characteristics of the incipient fault remain largely unknown. In this article, we report on the experimental simulation of an incipient fault according to actual operating scenarios and the measurement of both nonelectrical and electrical characteristics of the incipient fault. We then divide the incipient fault into three phases and further divide the start phase into three secondary phases, namely those relating to the predischarge, episodic discharge, and substable discharge (SSD). The dynamic characteristic of the liquid electrode in the incipient fault reveals that there is a certain stability when the SSD phase appears, which is considered the stage in which characteristics of the incipient fault can be extracted. The time-domain characteristics of the fault are somewhat unclear, while the harmonic content in the stage of the SSD is obviously clear and hardly changes with the further occurrence of incipient faults. This distinctive characteristic appears multiple times between the first incipient fault and the permanent fault and can be used to capture the appearance of incipient faults.