A method for processing a service flow in a packet network and applied to a network device group including a first network device and a second network device coupled to the first network device includes the first network device: obtaining a first upstream service flow; receiving a second upstream service flow from the second network device; obtaining a third upstream service flow based on a first reference sequence number, a sequence number included in each upstream data packet in the first upstream service flow, and a sequence number included in each upstream data packet in the second upstream service flow, where a sequence number included in any upstream data packet in the third upstream service flow is greater than the first reference sequence number; and sending the third upstream service flow to a next hop node.