The invention relates to a water seepage warning system applied to a mechanism box of a transformer substation. The system includes a microprocessor, a communication device, a water sensing device, awarning device and a terminal; the terminal is arranged outside the mechanism box and electrically connected with the communication device; the communication device, the water sensing device and the warning device are electrically connected with the microprocessor separately. According to the provided water seepage warning system applied to the mechanism box of the transformer substation, througharrangement of the water sensing device, the communication device and the terminal, real-time detection of a water seepage problem of the mechanism box is achieved, positioning of the mechanism box having the water seepage problem is conducted according to a feedback signal, and the work efficiency of workers is improved.