An on-line integrated fault diagnosis method of power grid based on three-state（steady， dynamic and transient state）data is proposed. Firstly， proceeding from the data characteristic and the status quo of dispatch automation， an analysis is made of the necessity of on-line fault diagnosis using the three state data. Secondly， starting from the aspects of accuracy， real-time， comprehensiveness of on-line fault diagnosis， a technology of data mining and co-processing based on multi-source information is proposed. Lastly， a look-ahead of the future developing direction in the field of on-line fault diagnosis is given.