A method of transmitting power information in a wireless communication system is provided. The method includes: determining energy per resource element (RE) to which a reference signal or data is mapped for downlink transmission; and transmitting power information of the reference signal and the data, wherein the reference signal comprises a channel state indication-reference signal (CSI-RS) for channel state measurement, power information of the CSI-RS is denoted by a ratio of power for a CSI-RS RE and power for a data RE of an orthogonal frequency division multiplexing (OFDM) symbol on which only data is transmitted or power for a cell-specific RS (CRS) RE used for channel state measurement and data demodulation of different OFDM symbols.