A method and device for realizing data transmission, including: when a starting condition of a timer of a packet data convergence protocol (PDCP) of a data receiving side is satisfied, starting the timer of the PDCP of the data receiving side, and receiving and reordering data within a duration of the timer; and when a stopping condition of the timer of the PDCP of the data receiving side is satisfied, stopping the timer, and delivering to an upper layer the reordered data that has been processed; wherein the duration of the timer is related to a radio link control (RLC) mode of an offloading bearer. In embodiments of the present document, by setting the starting condition of the timer of the PDCP at the data receiving side, data packets are received and reordered within the duration of the timer when the data packets are received, and the timer is stopped while the data packets are continuously delivered when the stopping condition of the timer is satisfied, which realizes efficient ordered transmission of the data packets of the PDCP.