The invention discloses an insulator fault indicator which comprises a fault indicator shell and a current mutual inductance coil, a large-current protection circuit, a signal indicating circuit and a signal indicator which are arranged in the fault indicator shell. A connecting hole is formed in the fault indicator shell, and the fault indicator shell sleeves a lower connecting shaft of an insulator; the current mutual inductance coil sleeves a ground lead of the insulator from outside, and the current mutual inductance coil, the large-current protection circuit, the signal indicating circuit and the signal indicator are sequentially connected. By the arrangement, when overvoltage formed at two ends of the insulator are punctured, a current transformer detects current of the ground lead of the insulator and sends signals to the signal indicating circuit, the signal indicating circuit controls the signal indicator to send insulator fault information to the outside, manual intervention is not needed, the entire process is automatically performed, the fault insulator can be found by engineering maintenance personnel conveniently and replaced, and maintenance efficiency is greatly improved.