Abstract: The paper put forward a design scheme of on-line calculation and analysis management system of theory line loss of power grid based on Web issue, introduced architecture and functions implementation of the system. The system uses SCADA system to obtain real-time data of power grid, and adopts data mining and data clustering algorithm to realize autofilter of the real-time data, and uses Web method to issue and summary calculation results of theory line loss of power grid, which can provide a good platform for fully grasping status of line loss of power gird and proposing reduction loss measures.