A method for sending a Channel State Information (CSI) report for a Downlink (DL) channel by a User Equipment (UE) in a mobile communication system is provided. The method includes obtaining, from an evolved Node B (eNB), CSI report setting information including information about a transmission cycle and a transmission time for a CSI report, and Discontinuous Reception (DRX) setting information including information about an active time period in which signal transmission/reception is available in a DRX mode, determining whether the UE operates in the DRX mode, and if the UE is determined to operate in the DRX mode, adjusting the transmission time taking into account the CSI report setting information and the active time period, and sending the CSI report at the adjusted transmission time.