A method and apparatus for transmitting a downlink signal in a wireless communication system are disclosed. An apparatus for receiving a downlink (DL) signal from a base station (BS) and transmitting the received DL signal to a user equipment (UE) in a wireless communication includes: a plurality of reception antennas configured to receive DL signals from the BS; a processor configured to map the received DL signals to at least one transmission antenna; and a plurality of transmission antennas configured to transmit the received DL signals to the UE, wherein the processor is configured to select M transmission antenna(s) from among the plurality of transmission antennas (Ntx,REP Tx antennas), and map the received L signals to the M transmission antenna(s), and the number of the transmission antennas (Ntx,REP) is higher than the number of the reception antennas (Nrx,REP), and M is the number of the transmission antennas which is used to transmit the received DL signals.