Physical topology of low-voltage networks is unpredictable and its Power Line Communication (PLC) channel is changeable, reliability of communication limits badly the application scale of PLC in practice. In this paper, a new Router Algorithm is proposed for PLC. Considering the channel state which is exquisite change and the successful level which is very lower in communication, dynamic clustering based on node relevance is used. According to the intension of signal, the probability of communication and connectivity of node, the router selects cluster head and the members of cluster based on node relevance. In the stage of steady arithmetic, router completes the data collection through the way of fixed data transmission and gateway nodes initiating transmission. When the communication of some network nodes is unusual, the router adopts mechanism of probabilistic flooding based on the number of nearby nodes to rebuild network. This method can guarantee real-time data transmission. The analysis shows that this router has the flexibility, practicality and effectiveness.