Abstract: Through the classification and reasoning of alarm information of smart substation equipment in case of fault, the intelligent alarm of fault is realized. In this paper, the work flow of intelligent alarm is sorted out according to the severity level of alarm information in smart substation, the information is processed and displayed in different levels. Through the analysis of SCD configuration file in smart substation, the secondary-circuit network topology map of substation is drawn and correlated with alarm information, so as to narrow the location range of fault points. Through the intelligent alarm expert system, the inference knowledge base is established to locate and eliminate the fault quickly. The validity of the method is verified by a practical reasoning case.