A method and an apparatus for processing a modified packet. A first routing device obtains a first packet sent by a second routing device, where the first packet carries a first correspondence, creates a forwarding entry that includes the first correspondence, receives a modified packet and determines an ID of a destination service function (SF) of the modified packet, queries the forwarding entry according to the ID of the destination SF, and determines that an SF identified by the ID of the destination SF is an SF connected to a second routing device, and forwards the modified packet to the second routing device.