Embodiments of the present invention relate to the field of communications technologies and disclose a packet loss detection method, an apparatus, and a system. The method includes: collecting, by a first network device according to packets sent to a second network device, statistics on a first result corresponding to each group of packets, one first result includes a quantity of packets in one group of packets and a section identifier of the group of packets, each group of packets includes multiple packets, and multiple packets are continuously sent by first network device and belong to a section corresponding to a section identifier of the group of packet; sending, by first network device, first result corresponding to each group of packets to a controller according to a preset rule, so that controller determines whether a packet in the packets sent by first network device to second network device is lost.