The embodiments of the present invention provide a method, a device, and a system for forwarding a packet. The method includes: receiving an IPv6 packet sent by a gateway, and obtaining a flow label of the IPv6 packet, where the flow label of the IPv6 packet is corresponding to a link identity of customer premise equipment in one-to-one correspondence; decapsulating the IPv6 packet; performing network address translation on a decapsulated packet according to the flow label; and forwarding the decapsulated packet according to a translated network address. When multiple links between the gateway and an AFTR are corresponding to the same tunnel for network address translation, in the case that IP addresses of terminal users are overlapping or are the same, different terminal users can be distinguished, so that a terminal user that sends a packet can receive feedback, thus improving customer satisfaction.