A method for implementing multicast service is disclosed, comprising: a multicast source sending a multicast service packet of which a destination address is configured to be a Group Access Identity (GAID) assigned to the multicast source; an Access Service Router (ASR) to which the multicast source belongs searching for a corresponding Group Router Identity (GRID) in the established GAID-GRID mapping table according to the GAID, and sending the multicast service packet to a General Switch Router (GSR); the GSR searching for a corresponding multicast tree according to the GRID of the multicast service packet, and sending the multicast service packet to the ASR in the service area; the ASR in the service area searching for a corresponding GAID in the established GAID-GRID mapping table according to the GRID, and sending the multicast service packet to the terminal under the ASR in the service area.