A method for processing a modified packet, comprising: obtaining, by a first routing device, a first packet sent by a second routing device, wherein the first packet carries a first correspondence, the first correspondence comprises a correspondence between network address information of the second routing device and an identifier, ID, of a service function, SF, node connected to the second routing device, and the second routing device is connected to the first routing device; creating, by the first routing device, a forwarding entry, wherein the forwarding entry comprises the first correspondence, and the network address information of the second routing device in the forwarding entry indicates address information of a next-hop routing device of the first routing device on a service chain; receiving, by the first routing device, a modified packet, and determining an ID of a destination SF of the modified packet, wherein the modified packet is a packet to which an ID of a source SF of the modified packet or the ID of the destination SF is added and that is forwarded on the service chain; querying, by the first routing device, the forwarding entry according to the ID of the destination SF, obtaining the network address information of the second routing device from the first correspondence that matches the ID of the destination SF, and determining that an SF identified by the ID of the destination SF is the SF connected to the second routing device; and forwarding, by the first routing device, the modified packet to the second routing device according to the network address information of the second routing device. obtaining, by a first routing device, a first packet sent by a second routing device, wherein the first packet carries a first correspondence, the first correspondence comprises a correspondence between network address information of the second routing device and an identifier, ID, of a service function, SF, node connected to the second routing device, and the second routing device is connected to the first routing device; creating, by the first routing device, a forwarding entry, wherein the forwarding entry comprises the first correspondence, and the network address information of the second routing device in the forwarding entry indicates address information of a next-hop routing device of the first routing device on a service chain; receiving, by the first routing device, a modified packet, and determining an ID of a destination SF of the modified packet, wherein the modified packet is a packet to which an ID of a source SF of the modified packet or the ID of the destination SF is added and that is forwarded on the service chain; querying, by the first routing device, the forwarding entry according to the ID of the destination SF, obtaining the network address information of the second routing device from the first correspondence that matches the ID of the destination SF, and determining that an SF identified by the ID of the destination SF is the SF connected to the second routing device; and forwarding, by the first routing device, the modified packet to the second routing device according to the network address information of the second routing device.