A multicast packet forwarding method, to implement multicast forwarding of an IPv6 multicast data packet on an IPv4 network, thereby saving bandwidth of the IPv4 network. The method includes: receiving an MLD multicast group join packet that is sent by an ISATAP host, encapsulated in an IPv4 unicast packet, and used for joining an IPv6 multicast group; maintaining an IPv6 multicast forwarding table according to the MLD multicast group join packet; receiving an IPv6 multicast data packet that is sent by an IPv6 network device and corresponds to the IPv6 multicast group; encapsulating, according to an IPv6-IPv4 multicast group mapping relationship, the IPv6 multicast data packet in an IPv4 multicast data packet, and sending the IPv4 multicast data packet to an IPv4 device, so that the IPv4 device forwards the IPv4 multicast data packet to the ISATAP host.