A data packet detection method, a device, and a system are disclosed. The method includes: receiving first control information sent by a controller; receiving a first data packet sent by a previous-hop network device of a first network device, where the first data packet includes first detection information, and the first detection information includes a first detection node identifier, a first sequence number, and first collection information; determining, based on the first collection information, first collected data corresponding to the first collection information, and updating the first detection node identifier; and sending, to a next-hop network device of the first network device, the first data packet carrying the updated first detection information. This implements information telemetry on a data packet on a transmission path.