As to the problem of network topology discovery by the low-voltage power line carrier

spanning tree collection is used to deduce the migration of the tree

and to discover the communication network topology.The connected graph is also applied to illustrate and analyze smart meter nodes and the relations between those nodes.The decisional rules of relations of smart meter nodes is established and a low-voltage PCL network topology discovery algorithm is proposed based on spanning tree(STTDA). The critical factors and efficiency of the algorithm had also been analyzed.