An apparatus and a method of measuring a reference signal for efficient downlink transmission in a mobile communication system are provided. The system includes plural base stations, each having a plurality of antennas distributed in the service area thereof based on a Distributed Antenna System (DAS). A method for a base station to notify a terminal of reference signal measurement information in a mobile communication system comprises determining whether the terminal is in a Rank Indicator/Precoding Matrix Indicator (RI/PMI) disabled mode, selecting, when the terminal is in the RI/PMI disabled mode, the reference signal to be measured by the terminal between a Cell-specific Reference Signal (CRS) and a Channel Status Information Reference Signal (CSI-RS), notifying the terminal of the reference signal measurement information with the selection result, and receiving channel information generated based on the reference signal measurement information from the terminal.