This application provides a packet processing method, a device and a system. The system includes a layer 4 forwarding device, a layer 7 forwarding device, and a controller. The controller sends a first forwarding entry to the layer 4 forwarding device, where the first forwarding entry includes a first keyword and a first processing policy corresponding to the first keyword, the first keyword includes layer 4 information for matching a packet, and the first forwarding entry is used to instruct the layer 4 forwarding device to send a second packet to the layer 7 forwarding device according to the first processing policy when a first packet matching the first keyword is received; and the controller sends, to the layer 7 forwarding device, a control rule used to instruct the layer 7 forwarding device in packet processing.