Embodiments of the present invention provide a power control method, device, and system, and relate to the field of communications technologies. The method is applied to a vectoring system, where the vectoring system includes multiple lines, each line includes multiple subcarriers, and for each subcarrier, a crosstalk channel is formed between the multiple lines, and the method includes: obtaining a closed subcarrier set of the multiple lines according to line crosstalk channel information corresponding to each subcarrier of the multiple subcarriers, where the closed subcarrier set includes a subcarrier set required to be closed on the multiple lines; and sending the closed subcarrier set of the multiple lines to a transceiver, and closing, by the transceiver, a transmit signal on a subcarrier required to be closed on each line.