The invention relates to an online monitoring and condition maintenance management system, which is a layered and distributed data management and computer system, faces to a plurality of substation high-voltage equipment and adopts a multi-server level-to-level management system. The online monitoring and condition maintenance management system comprises an online monitoring equipment layer, a substation data network layer and a remote data center. By constructing and applying the management system, the online monitoring system is promoted to be transitioned to an all-round, networked, intelligent and comprehensive condition monitoring, diagnosis and service management system from the traditional isolated and static experimental system. The system provides a powerful technical supporting platform for overcoming periodic maintenance blindness, reducing maintenance times, reducing maintenance expenses, delaying maintenance cycle to the utmost extent, truly realizing condition maintenance for power system operation and management departments and further improving the operation rate of the equipment and the safety of power grids.