The invention provides an on-line monitoring fault diagnosis system and method for an artificial neural network high voltage circuit breaker. The system comprises a DSP, a current transformer, a voltage transformer, a temperature sensor, a vibration sensor, a speed sensor, an A/D conversion circuit, voltage conversion, optocoupler isolation, a programming interface, a resetting unit, a display driver, a display unit, an alarm unit, an operation panel, a communication unit, an industrial computer, a memory, a printer and a high voltage circuit breaker. According to the invention, the development of on-line monitoring and fault diagnosis technologies of the high voltage circuit breaker are greatly improved, and the system and method lay the foundation for the development of intelligent electrical appliance and intelligent power grid technologies.