Abstract: In order to improve fault diagnosis level of high-voltage circuit breaker, the method of using D-S evidence theory to fuse data obtained by different types of sensors was researched and it was used in fault diagnosis for high-voltage circuit breaker. Analysis of an actual example showed that D-S evidence theory can improve speed, correctness and reliability of fault diagnosis for high-voltage circuit breaker, and the more fused data there is, the higher reliability of fault diagnosis is. Besides, the method has universality.