The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4th-Generation (4G) communication system such as Long Term Evolution (LTE). The present disclosure discloses a system, a data transmission method and a network equipment supporting a Packet Data Convergence Protocol (PDCP) duplication function. The data transmission method supporting a PDCP duplication function comprises the steps of: transmitting, by a first network equipment, a configuration instruction message of a radio bearer supporting a PDCP duplication function to a second network equipment; and, performing, by the first network equipment and the second network equipment, transmission of a data packet of the radio bearer configured with the PDCP duplication function. In the present disclosure, by an interface between the first network equipment and the second network equipment, the transmission of duplicated data packets between the first network equipment and the second network equipment is realized, and the reliability of data transmission is improved. The present disclosure also discloses a method and device for transferring supplementary uplink carrier configuration information and a method and device for performing a connection mobility adjustment.