A novel fault diagnosis model for circuit breaker based on power dispatching system is designed in this paper. The model has three levels including data level, criterion level and judging level. The data level consists of data obtaining, data handling and fault database. The criterion level consists of operating time characteristics model, fault tree and repository. The judging level is logical judging method. To establish fault diagnosis model based on power dispatching system, this paper introduces a compensation parameter "△t" which is a key parameter of operating time characteristics model. The compensation parameter "△t" is proved to be stable and useful by large numbers of tests. Therefore, the operating time characteristics model can be an effective part of fault diagnosis model. As a result, the fault diagnosis model based on power dispatching system would be an efficient way to judge fault for circuit breaker.