A handover control method, comprising: receiving (201, 401, 503, 803), by a terminal device, a first message sent by a source base station, wherein the first message comprises information about at least one downlink first unacknowledged service data unit, SDU, of a packet data convergence protocol, PDCP, the first message is used to instruct the terminal device to be handed over to a target base station, and the information about the at least one downlink first unacknowledged SDU of the PDCP is used to indicate a sequence number, SN, of a downlink PDCP SDU that is the first one of SDUs that are of at least one source data radio bearer, DRB, for communication between the terminal device and the source base station before the handover and that are not correctly received by the terminal device; completing (203, 403, 505, 805), by the terminal device, the handover, to access the target base station; and receiving (204, 404, 506, 806), by the terminal device, downlink PDCP SDUs of the at least one source DRB that are not correctly received by the terminal device in sequence and that are numbered from the SN indicated by the information about the at least one downlink first unacknowledged SDU of the PDCP, wherein the downlink PDCP SDUs of the at least one source DRB are retransmitted by the target base station; wherein 7 the first message further comprises information about the last downlink PDCP SDUs of a plurality of source DRBs between the terminal device and the source base station that are remapped during handover preparation to one target DRB for communication between the terminal device and the target base station, and the information is used to indicate SNs of the last downlink PDCP SDUs that are of the plurality of DRBs for communication between the terminal device and the source base station before the handover and that are not correctly received by the terminal device. receiving (201, 401, 503, 803), by a terminal device, a first message sent by a source base station, wherein the first message comprises information about at least one downlink first unacknowledged service data unit, SDU, of a packet data convergence protocol, PDCP, the first message is used to instruct the terminal device to be handed over to a target base station, and the information about the at least one downlink first unacknowledged SDU of the PDCP is used to indicate a sequence number, SN, of a downlink PDCP SDU that is the first one of SDUs that are of at least one source data radio bearer, DRB, for communication between the terminal device and the source base station before the handover and that are not correctly received by the terminal device; completing (203, 403, 505, 805), by the terminal device, the handover, to access the target base station; and receiving (204, 404, 506, 806), by the terminal device, downlink PDCP SDUs of the at least one source DRB that are not correctly received by the terminal device in sequence and that are numbered from the SN indicated by the information about the at least one downlink first unacknowledged SDU of the PDCP, wherein the downlink PDCP SDUs of the at least one source DRB are retransmitted by the target base station; wherein 7 the first message further comprises information about the last downlink PDCP SDUs of a plurality of source DRBs between the terminal device and the source base station that are remapped during handover preparation to one target DRB for communication between the terminal device and the target base station, and the information is used to indicate SNs of the last downlink PDCP SDUs that are of the plurality of DRBs for communication between the terminal device and the source base station before the handover and that are not correctly received by the terminal device.