A forward error correction codeword synchronization method, comprising: after a terminal device initiates an access or registration request to a central office device, receiving (S101;S302) synchronization information that is of a first forward error correction, FEC, codeword and is sent by the central office device by using a management channel, wherein the synchronization information of the first FEC codeword comprises information about an agreed location of the first FEC codeword, and the information about the agreed location of the first FEC codeword indicates a location that is of the first FEC codeword and is corresponding to data at an agreed location of an agreed time-frequency resource block; resetting (S102;S303) a status parameter of a terminal decoder according to the synchronization information of the first FEC codeword, so that the terminal decoder starts decoding from the agreed location of the first FEC codeword, or resetting a status parameter of a terminal encoder according to the synchronization information of the first FEC codeword, so that the location that is of an FEC codeword output by the terminal encoder and is corresponding to the data at the agreed location of the agreed time-frequency resource block is the same as the agreed location of the first FEC codeword; and characterized by: when the location that is of the FEC codeword input by the terminal decoder and is corresponding to the data at the agreed location of the agreed time-frequency resource block is different from the agreed location of the first FEC codeword, that is, the FEC codeword is unsynchronized, sending a resynchronization request to the central office device; receiving the synchronization information that is of the first FEC codeword and is resent by the central office device by using the management channel; and resetting status data of the terminal encoder, so that the location that is of an FEC codeword output by the terminal encoder and is corresponding to the data at the agreed location of the agreed time-frequency resource block is the same as the agreed location of the first FEC codeword, so as to complete codeword synchronization again. after a terminal device initiates an access or registration request to a central office device, receiving (S101;S302) synchronization information that is of a first forward error correction, FEC, codeword and is sent by the central office device by using a management channel, wherein the synchronization information of the first FEC codeword comprises information about an agreed location of the first FEC codeword, and the information about the agreed location of the first FEC codeword indicates a location that is of the first FEC codeword and is corresponding to data at an agreed location of an agreed time-frequency resource block; resetting (S102;S303) a status parameter of a terminal decoder according to the synchronization information of the first FEC codeword, so that the terminal decoder starts decoding from the agreed location of the first FEC codeword, or resetting a status parameter of a terminal encoder according to the synchronization information of the first FEC codeword, so that the location that is of an FEC codeword output by the terminal encoder and is corresponding to the data at the agreed location of the agreed time-frequency resource block is the same as the agreed location of the first FEC codeword; and characterized by: when the location that is of the FEC codeword input by the terminal decoder and is corresponding to the data at the agreed location of the agreed time-frequency resource block is different from the agreed location of the first FEC codeword, that is, the FEC codeword is unsynchronized, sending a resynchronization request to the central office device; receiving the synchronization information that is of the first FEC codeword and is resent by the central office device by using the management channel; and resetting status data of the terminal encoder, so that the location that is of an FEC codeword output by the terminal encoder and is corresponding to the data at the agreed location of the agreed time-frequency resource block is the same as the agreed location of the first FEC codeword, so as to complete codeword synchronization again. when the location that is of the FEC codeword input by the terminal decoder and is corresponding to the data at the agreed location of the agreed time-frequency resource block is different from the agreed location of the first FEC codeword, that is, the FEC codeword is unsynchronized, sending a resynchronization request to the central office device; receiving the synchronization information that is of the first FEC codeword and is resent by the central office device by using the management channel; and resetting status data of the terminal encoder, so that the location that is of an FEC codeword output by the terminal encoder and is corresponding to the data at the agreed location of the agreed time-frequency resource block is the same as the agreed location of the first FEC codeword, so as to complete codeword synchronization again.