For converging a 5th-Generation (5G) communication system and supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT), a channel state information (CSI) acquisition method includes transmitting CSI configuration information to a terminal, selecting a beam for transmitting a beamformed CSI reference signal (BF-CSI-RS) to the terminal, transmitting the BF-CSI-RS to the terminal using the selected beam, and notifying the terminal of a beamforming update. A base station for acquiring CSI in a mobile communication system includes a transceiver configured to transmit and receive signals, and a controller configured to control the transceiver to transmit CSI configuration information to a terminal, to select a beam for transmitting a BF-CSI-RS to the terminal, to transmit the BF-CSI-RS to the terminal using the selected beam, and to notify the terminal of a beamforming update.