The technology of online monitoring for electrical equipment is mature, but the data the system provided is too professional to read. Also the course of electrical equipment status change often lasts very long time. The changing in numeric is too small to notice the problem of equipment. By acquiring and processing different kinds of data, such as real-time data, historic data, off-line data from management information system and manual intervention data, this paper applies key performance indicator (KPI) in online monitoring system to provide more readable results of electrical equipment status. The new system has been applied in many smart substation and got positive response.