In order to guarantee the accuracy of the fault diagnosis results when actual protections and breakers wrongly act， or the relevant alarms lost and so on， a new fault diagnosis method is proposed. In this method， a typical optimization model based on telemetering data is developed with the guidance of set cover theory. And a wavelet technique is used to analyze the fault recorder information. Finally， results of the above two methods are fused with the improved evidence theory， and therefore the accurate diagnosis results are obtained. The effectiveness of the proposed method has been proved on RTDS.