A method and an apparatus for improving power output efficiency of a line driver are disclosed. The method includes: obtaining a current working parameter of an xDSL subscriber board, where the current working parameter includes at least one of a working mode configured on a subscriber port of the xDSL subscriber board and current output power of the subscriber port; and determining, according to the current working parameter, a control signal for a line driver in the xDSL subscriber board and outputting the control signal.