Provided are a line initialization method, device and system. The method comprises: when a new line is added, releasing at least one resource unit which is located on a line in the stage of Showtime, so that the line which is in the stage of Showtime transmits data on remaining resource units after releasing at least one resource unit; performing basic initialization on the new line using at least one resource unit or a subset of a set formed by at least one resource unit, so that the new line can transmit data after the basic initialization using at least one resource unit or the subset formed by at least one resource unit; and performing crosstalk offset initialization on the line which is in the stage of Showtime and the new line using all the resource units, so that the new line is initialized to be a line which is in the stage of Showtime. Compared with the prior art, the time for initializing the new line is shorter in the embodiments of the present invention, and the new line may have a data transmission ability in a relatively short time.