A multicast transmission method for Over The Top, OTT, media, comprising: after receiving, from a terminal player or a downloading module in a terminal, a request for media description information corresponding to OTT media, requesting, by a terminal proxy module in the terminal, the media description information from a multicast control module on a multicast server; by the multicast control module on the multicast server, acquiring the media description information from an OTT media server, adding multicast information in the media description information, and returning the media description information added with the multicast information to the terminal proxy module in the terminal, wherein the multicast information comprises multicast group information, and the media description information comprises a media index file address and/or a media content file address; by the terminal proxy module in the terminal, modifying the media index file address and/or the media content file address in the media description information into a local address of the terminal, returning the media description information to the terminal player or the downloading module in the terminal, and transferring the multicast information to a multicast receiving module in the terminal; joining, by the multicast receiving module in the terminal, a multicast group according to the multicast information; by a multicast packing module on the multicast server, acquiring a media index file and/or a media content file from the OTT media server and packing the media index file and/or the media content file into a multicast packet; sending, by a multicast sending module on the multicast server, the multicast packet to the corresponding multicast group; by a multicast receiving module in the terminal, receiving the multicast packet and transferring the received multicast packet to a multicast unpacking module in the terminal; restoring, by the multicast unpacking module in the terminal, the multicast packet to the media index file and/or the media content file; and after receiving a request, which is sent from the terminal player or the downloading module in the terminal according to the local address, for the media index file and/or the media content file, returning, by the terminal proxy module in the terminal, the media index file and/or the media content file restored by the multicast unpacking module in the terminal to the terminal player or the downloading module in the terminal; further comprising: acquiring, by the terminal proxy module in the terminal, the media index file and/or the media content file corresponding to the multicast packet from the OTT media server through unicast when the terminal is incapable of normally receiving the multicast packet from the multicast server according to the multicast group information. after receiving, from a terminal player or a downloading module in a terminal, a request for media description information corresponding to OTT media, requesting, by a terminal proxy module in the terminal, the media description information from a multicast control module on a multicast server; by the multicast control module on the multicast server, acquiring the media description information from an OTT media server, adding multicast information in the media description information, and returning the media description information added with the multicast information to the terminal proxy module in the terminal, wherein the multicast information comprises multicast group information, and the media description information comprises a media index file address and/or a media content file address; by the terminal proxy module in the terminal, modifying the media index file address and/or the media content file address in the media description information into a local address of the terminal, returning the media description information to the terminal player or the downloading module in the terminal, and transferring the multicast information to a multicast receiving module in the terminal; joining, by the multicast receiving module in the terminal, a multicast group according to the multicast information; by a multicast packing module on the multicast server, acquiring a media index file and/or a media content file from the OTT media server and packing the media index file and/or the media content file into a multicast packet; sending, by a multicast sending module on the multicast server, the multicast packet to the corresponding multicast group; by a multicast receiving module in the terminal, receiving the multicast packet and transferring the received multicast packet to a multicast unpacking module in the terminal; restoring, by the multicast unpacking module in the terminal, the multicast packet to the media index file and/or the media content file; and after receiving a request, which is sent from the terminal player or the downloading module in the terminal according to the local address, for the media index file and/or the media content file, returning, by the terminal proxy module in the terminal, the media index file and/or the media content file restored by the multicast unpacking module in the terminal to the terminal player or the downloading module in the terminal; further comprising: acquiring, by the terminal proxy module in the terminal, the media index file and/or the media content file corresponding to the multicast packet from the OTT media server through unicast when the terminal is incapable of normally receiving the multicast packet from the multicast server according to the multicast group information.