A data processing method, a device, and a system, for performing different processing on data packets of varying degrees of importance in a same service flow, where the data processing method includes: A first device receiving a first data packet from a third device, where the first data packet carries transmission requirement indication information of the first data packet, where the first device is any intermediate device between a source device and a target device that correspond to the first data packet, and where the third device is a previous-hop device adjacent to the first device on a transmission path from the source device to the target device; the first device determining, based on the transmission requirement indication information of the first data packet, a processing policy corresponding to the first data packet; and the first device processing the first data packet according to the processing policy.