Abstract: In the SCD of intelligent substations, the information of the Exchanger model is usually lacking, which leads to the incomplete topology diagram of the equipment and the breakpoints in the middle, which can not completely describe and display the actual network in the substations, especially the whole case of the secondary circuit. By identifying the key identification of the network secondary circuit and the switch itself, adding the corresponding switch information to the SCD file, and standardizing the network connection relationship, based on IEC61850, the IED device of switch port state and access port is modeled, and the relation of secondary virtual loop in SCD is combined to realize the dynamic monitoring of secondary virtual loop based on network topology and communication state. The virtual loop is visualized by using the graphic technology and the traditional secondary loop method. The traffic and IED information are sent to monitor whether there is any abnormal situation in each port.