The present invention provides a method and a device for line initialization. In the method, first, a first precoding matrix needed by a first part of subcarriers is acquired in a downstream direction, and then multiple data signals of all data signals that need to be sent in an initialization process are sent by using only the first part of subcarriers; afterward, a second precoding matrix needed by at least a second part of subcarriers of all available subcarriers is acquired, and remaining data signals of all the data signals exclusive of the multiple data signals are sent by using the at least second part of subcarriers to complete line initialization. By using the foregoing manner, the present invention can cancel crosstalk between lines while completing line initialization, and does not easily cause transmit power to exceed a limit.