The present invention provides a message processing method, device, and system. The method includes: receiving a TCP data acknowledgement message sent by a UE; obtaining, according to the TCP data acknowledgement message, an identifier of a TCP data packet successfully received by the UE; obtaining, according to correspondence between the identifier of the TCP data packet and an identifier of at least one RLC protocol AMD PDU, the identifier of the at least one RLC protocol AMD PDU corresponding to the identifier of the TCP data packet; and determining that the UE has successfully received the at least one RLC protocol AMD PDU corresponding to the identifier of the at least one RLC protocol AMD PDU.