By analyzing the interface and function specification of the on-line monitoring system in substation，the integrated modeling approach from on-line monitoring intelligent electronic devices（IED）to substation side monitoring unit and condition monitoring master station system is proposed.In view of the feature that the on-line monitoring system is mainly concerned about the entity information of primary equipment and its components，the power system resource class and asset class of the common information model are used to establish the power grid structure and primary equipment model of the on-line monitoring system in substations.In addition，to reduce the modeling workload and ensure the consistency of model，the implementation scheme for achieving model sharing between substation side monitoring unit and condition monitoring master station system is also given.Based on the model of IEC61850，the condition monitoring data access specification is extended，the equipment parameter and data model of on-line monitoring IED and substation side monitoring unit are developed，and the approach to realizing the data mapping between on-line monitoring IED and substation side monitoring unit is given to perform source-end maintenance of the on-line monitoring data model.