Abstract: In order to solve the problems of large memory, long time consuming and low efficiency of traditional algorithm for searching live-line state inpower supply line monitoring and control, this paper proposed a color flow algorithm. The paper analyzed the structural characteristics of power supply lines of single power supply and dual power supply modes, defined color flow source, color flow tube and color flow valve by referring to the flow of electric current, deduced the algorithm of searching, analyzing, judging and coloring for the live-line state of power supply lines and equipment, and applied the monitoring and control system based on the algorithm to the operation state monitoring and control of Macheng—HuangpiRailway Power Transmission Line. The practice result shows that the state monitoring of the power supply line based on the color flow algorithm is no longer necessary to extract electrical signals with voltage and current transformers, which simplifies the monitoring and control device and saves the investment cost of the monitoring device. Compared with the traditional state search algorithm, the color flow algorithm is simpler, the search steps are less, the computer memory is small, and the running speed is fast, which improves the monitoring and control efficiency.