The invention discloses an electric control box fire on-line monitoring and automatic fire extinguishing system. The system comprises an electric control box body, a fire extinguishing box, a centralprocessing unit, a fire extinguisher bottle, a rechargeable storage battery, an infrared thermal imaging sensor, a smoke sensor and a fire extinguishing agent mobile spraying device; the fire extinguishing box is arranged at the edge of one side of the electric control box body; the fire extinguisher bottle is arranged in the fire extinguishing box; the fire extinguisher bottle is fixedly connected with the inner wall of the fire extinguishing box; the central processing unit is arranged in the fire extinguishing box; the rechargeable storage battery which can be matched with the central processing unit is arranged at the bottom in the fire extinguishing box; and the rechargeable storage battery is electrically connected with the central processing unit. The infrared thermal imaging sensorand the smoke sensor are arranged in an electric control box, so that real-time monitoring is capable of being carried out in the electric control box, and a fire is capable of being found in the first time; and the fire can be controlled and extinguished in the first time by arranging the fire extinguishing agent mobile spraying device, so that safety is improved, and the loss is reduced.