A method by a terminal in a communication system and an apparatus therefor are disclosed. The method includes receiving, from a base station, a radio resource control (RRC) message including a radio link control (RLC) configuration and a packet data convergence protocol (PDCP) configuration associated with a packet duplication, identifying whether a PDCP packet data unit (PDU) is a PDCP control PDU in case that the packet duplication is activated, and transmitting, to the base station, the PDCP control PDU without the packet duplication through a primary RLC entity based on the PDCP configuration in case the PDCP PDU is the PDCP control PDU. The disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates with a technology for internet of things (IoT), and may be applied to intelligent services based on the 5G communication technology and the IoT-related technology.