A method for mapping, by a base station, a channel state information reference signal (CSI RS) in a wireless communication system, the method comprising: generating the CSI for eight antenna ports; selecting a resource element (RE) set from a plurality of RE sets in a subframe using an extended cyclic prefix (CP), wherein the selected RE set includes four pairs of REs in consecutive orthogonal frequency division multiplexing (OFDM) symbols, and wherein the four pairs of REs are separated from each other by constant subcarrier spacing in the consecutive OFDM symbols; and mapping the CSI RS for the eight antenna ports to the selected RE set.