A method for constructing a multipath forwarding rule, an apparatus, and a system. A controller invokes a multipath algorithm to generate multiple paths for a data stream; the controller generates a multiport rule of a forwarding device according to the multiple paths; the controller generates metadata according to the multiport rule of each forwarding device, where the metadata includes information for indicating at least one forwarding port of the forwarding device; the controller generates a flow entry establishment indication; the controller sends the flow entry establishment indication to a forwarding device, such that each forwarding device selects the at least one forwarding port of the forwarding device according to the flow entry establishment indication, to forward the data stream.