Embodiments of the present invention relates to the field of communications, which complements a data forwarding method of a backup incoming interface under protocol independent multicast dual join in a PIM protocol, facilitates implementation of compatibility in various manufacturers, and reduces a restriction of a network topology on the application of the PIM protocol. The method includes: when a main incoming interface is up, forwarding, by a router, multicast data received from a backup incoming interface to the main incoming interface in a join state; and when the main incoming interface is down, before selecting a new main incoming interface and/or backup incoming interface, forwarding, by the router, the multicast data received from the backup incoming interface to all interfaces in a join state or to all other interfaces in a join state except the backup incoming interface.