With the development of fiber optical communication， the power line carrier（PLC） communication is gradually becoming an auxiliary method in electric power communication. Most of the PLC channels have already been replaced by fiber channels and a lot of unused line traps have increased the electric energy loss. Based on an analysis of the high-frequency carrier channel structure and frequency allocation pattern，the graph theory is applied to establish a graphic modeling. The improved breadth-first traverse algorithm is used to search for the shortest path between two co-frequency use carrier channels influenced by unloading traps. By calculating the signal-to-crosstalk ratio of co-frequency use carrier channels in the shortest path， the decision on unloading traps is made. The accounting method is improved to make the accounting target more practical and examples are given to demonstrate the correctness of the method.