A data transmission method, comprising the steps of: receiving, by a transmitting device, indication information, wherein the indication information is used for indicating switching a Data Radio Bearer, DRB, corresponding to a first Quality of Service, QoS, flow from a first DRB to a second DRB; wherein the indication information is a Radio Resource Control, RRC, signaling or a Reflective Quality of Service, RQoS, wherein the RQoS is determined according to an Identity, ID, of a data packet received on the second DRB; switching, by the transmitting device, the DRB corresponding to the first QoS flow from the first DRB to the second DRB (S210); and sending, by the transmitting device, unsent data packets in the first QoS flow to a receiving device through the second DRB (S220); wherein before the transmitting device switches the DRB corresponding to the first QoS flow from the first DRB to the second DRB, the method further comprises: sending, by the transmitting device, a first identity packet after sending at least one data packet in the first QoS flow through the first DRB, wherein the first identity packet is used for indicating that a previous data packet of the first identity packet is a last data packet corresponding to the first DRB; wherein, the first identity packet is a Service Data Adaptation Protocol, SDAP, Protocol Data Unit, PDU, without payload or an SDAP control PDU. receiving, by a transmitting device, indication information, wherein the indication information is used for indicating switching a Data Radio Bearer, DRB, corresponding to a first Quality of Service, QoS, flow from a first DRB to a second DRB; wherein the indication information is a Radio Resource Control, RRC, signaling or a Reflective Quality of Service, RQoS, wherein the RQoS is determined according to an Identity, ID, of a data packet received on the second DRB; switching, by the transmitting device, the DRB corresponding to the first QoS flow from the first DRB to the second DRB (S210); and sending, by the transmitting device, unsent data packets in the first QoS flow to a receiving device through the second DRB (S220); wherein before the transmitting device switches the DRB corresponding to the first QoS flow from the first DRB to the second DRB, the method further comprises: sending, by the transmitting device, a first identity packet after sending at least one data packet in the first QoS flow through the first DRB, wherein the first identity packet is used for indicating that a previous data packet of the first identity packet is a last data packet corresponding to the first DRB; wherein, the first identity packet is a Service Data Adaptation Protocol, SDAP, Protocol Data Unit, PDU, without payload or an SDAP control PDU. sending, by the transmitting device, a first identity packet after sending at least one data packet in the first QoS flow through the first DRB, wherein the first identity packet is used for indicating that a previous data packet of the first identity packet is a last data packet corresponding to the first DRB; wherein, the first identity packet is a Service Data Adaptation Protocol, SDAP, Protocol Data Unit, PDU, without payload or an SDAP control PDU. <EOS>