A method for obtaining key information during fast channel switching, comprising: receiving (A 1, 401), by a retransmission server, a fast channel switching request sent by a terminal; wherein the fast channel switching request comprises Synchronization Source, SSRC, of a media source; generating (A2, 402), by the retransmission server, according to the fast channel switching request, at least one unicast Real-time Transport Protocol RTP packet bearing key information and an RTP unicast pulse consisting of a plurality of RTP unicast pulse packets; wherein the key information refers to configuration information required for initialization of a demultiplexer or a decoder, wherein the unicast RTP packet bearing the key information uses a different SSRC from the SSRC of the media source, and the SSRC of the RTP unicast pulse packet is the same as the SSRC of the media source; sending (A3, 403), by the retransmission server, a fast channel switching response message to the terminal, wherein the response message comprises the SSRC of the unicast RTP packet bearing the key information, the sequence number of the first unicast RTP packet bearing the key information, the number of unicast RTP packets bearing the key information, the SSRC of the unicast pulse packet, and the sequence number of the first RTP unicast pulse packet; and sending (A4, 405), by the retransmission server, to the terminal, the at least one unicast RTP packet bearing the key information; receiving, by the retransmission server, a data retransmission request sent by the terminal, wherein the data retransmission request comprises SSRC information of the terminal, the SSRC information of the unicast RTP packet bearing the key information, the sequence number of a lost RTP packet bearing the key information, and the number of packets continuously lost after the RTP packet with the specified sequence number; sending, by the retransmission server, to the terminal, the lost RTP packet bearing the key information which is requested by the terminal through the retransmission request. receiving (A 1, 401), by a retransmission server, a fast channel switching request sent by a terminal; wherein the fast channel switching request comprises Synchronization Source, SSRC, of a media source; generating (A2, 402), by the retransmission server, according to the fast channel switching request, at least one unicast Real-time Transport Protocol RTP packet bearing key information and an RTP unicast pulse consisting of a plurality of RTP unicast pulse packets; wherein the key information refers to configuration information required for initialization of a demultiplexer or a decoder, wherein the unicast RTP packet bearing the key information uses a different SSRC from the SSRC of the media source, and the SSRC of the RTP unicast pulse packet is the same as the SSRC of the media source; sending (A3, 403), by the retransmission server, a fast channel switching response message to the terminal, wherein the response message comprises the SSRC of the unicast RTP packet bearing the key information, the sequence number of the first unicast RTP packet bearing the key information, the number of unicast RTP packets bearing the key information, the SSRC of the unicast pulse packet, and the sequence number of the first RTP unicast pulse packet; and sending (A4, 405), by the retransmission server, to the terminal, the at least one unicast RTP packet bearing the key information; receiving, by the retransmission server, a data retransmission request sent by the terminal, wherein the data retransmission request comprises SSRC information of the terminal, the SSRC information of the unicast RTP packet bearing the key information, the sequence number of a lost RTP packet bearing the key information, and the number of packets continuously lost after the RTP packet with the specified sequence number; sending, by the retransmission server, to the terminal, the lost RTP packet bearing the key information which is requested by the terminal through the retransmission request.