In order to improve the operation quality of the high voltage circuit breaker effectively

and to realize the reliable condition maintenance

a kind of on-line monitoring system for mechanical condition of vacuum circuit breaker based on vibration signal is designed. Overall structure of the monitoring system is designed in terms of satisfaction of overall demand of the system. And the front-end acquisition system for vibration signal is built based on YD37 accelerometer and PCI8192 data acquisition card. In the back-end signal processing

a stable feature vector is built which effectively combined with wavelet analysis

ensemble empirical mode decomposition（EEMD）and time domain features. And the distance discriminant analysis of the typical mechanical fault diagnosis of circuit breaker is used

the correct rate is above 95 %. The man-machine interface of the system is designed based on Lab VIEW

which is simple and beautiful

and can be operated.