A method and apparatus for transmitting a signal to a relay at a Base Station (BS) in a wireless communication system are disclosed. The method includes mapping a Reference Signal (RS) to a subframe having two slots, and transmitting the subframe to the relay. Each of the slots includes a plurality of consecutive resource elements over which the RS can be spread and the plurality of consecutive resource elements are overlapped with a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of the slot. If a last OFDM symbol of the subframe is not available to the relay, the RS is transmitted only in a first slot of the subframe.