A method for transmitting data, comprising: determining, by a receiving end, whether delivered data and data to be delivered are continuous according to window information of a reordering window and information of the delivered data, wherein the delivered data is a Service Data Unit, SDU, last delivered by a first layer of the receiving end to an upper layer of the receiving end, wherein the data to be delivered is received by the first layer, wherein the window information of the reordering window comprises a window lower bound identification of the reordering window, wherein the window lower bound identification of the reordering window is either a sequence number, SN, of a next Protocol Data Unit, PDU, waiting to be received, or a next SN of a highest SN in a received PDU; starting, by the receiving end, a timer of a first delivery mode when determining that the delivered data and the data to be delivered are not continuous, wherein the first delivery mode indicates that the receiving end directly delivers data to the upper layer upon receipt of the data; and delivering, by the receiving end, the data to be delivered to the upper layer using the first delivery mode until the timer of the first delivery mode expires or is stopped; when the timer of the first delivery mode is an expired state or a stopped state, delivering, by the receiving end, the data to be delivered to the upper layer using a second delivery mode, wherein the second delivery mode indicates that the receiving end delivers data to the upper layer in order; wherein the determining, by the receiving end, whether the delivered data and the data to be delivered are continuous according to the window information of the reordering window and the information of the delivered data, comprises: determining that the delivered data and the data to be delivered are not continuous if a count value corresponding to the window lower bound identification is not equal to a count value corresponding to a next SN of the SN of the last delivered SDU; or determining that the delivered data and the data to be delivered are continuous if the count value corresponding to the window lower bound identification is equal to the count value corresponding to the next SN of the SN of the last delivered SDU. determining, by a receiving end, whether delivered data and data to be delivered are continuous according to window information of a reordering window and information of the delivered data, wherein the delivered data is a Service Data Unit, SDU, last delivered by a first layer of the receiving end to an upper layer of the receiving end, wherein the data to be delivered is received by the first layer, wherein the window information of the reordering window comprises a window lower bound identification of the reordering window, wherein the window lower bound identification of the reordering window is either a sequence number, SN, of a next Protocol Data Unit, PDU, waiting to be received, or a next SN of a highest SN in a received PDU; starting, by the receiving end, a timer of a first delivery mode when determining that the delivered data and the data to be delivered are not continuous, wherein the first delivery mode indicates that the receiving end directly delivers data to the upper layer upon receipt of the data; and delivering, by the receiving end, the data to be delivered to the upper layer using the first delivery mode until the timer of the first delivery mode expires or is stopped; when the timer of the first delivery mode is an expired state or a stopped state, delivering, by the receiving end, the data to be delivered to the upper layer using a second delivery mode, wherein the second delivery mode indicates that the receiving end delivers data to the upper layer in order; wherein the determining, by the receiving end, whether the delivered data and the data to be delivered are continuous according to the window information of the reordering window and the information of the delivered data, comprises: determining that the delivered data and the data to be delivered are not continuous if a count value corresponding to the window lower bound identification is not equal to a count value corresponding to a next SN of the SN of the last delivered SDU; or determining that the delivered data and the data to be delivered are continuous if the count value corresponding to the window lower bound identification is equal to the count value corresponding to the next SN of the SN of the last delivered SDU. determining that the delivered data and the data to be delivered are not continuous if a count value corresponding to the window lower bound identification is not equal to a count value corresponding to a next SN of the SN of the last delivered SDU; or determining that the delivered data and the data to be delivered are continuous if the count value corresponding to the window lower bound identification is equal to the count value corresponding to the next SN of the SN of the last delivered SDU.