A method for transmitting a header-compressed packet based on a retransmission mechanism is disclosed according to the present disclosure. The method mainly includes: a header compressor of a sending device obtains feedback information of a header-compressed packet in a transmission process; and the header compressor determines a state of the header compressor according to the feedback information, compresses a header for the packet according to the state of the header compressor, and sends the packet to a decompressor of a receiving device. According to the present disclosure, a header compression mechanism is combined with an automatic retransmission mechanism, so that the header compressor obtains feedback information of an automatic retransmission technology, and estimates the decompression information of the decompressor correctly, so as to change a state machine of the header compressor at proper time and improve transmission efficiency of the packet.