A packet processing method includes receiving a first packet by a first receiving interface of a media conversion module of a first network device, where the first packet includes a first alignment marker (AM), sending a second packet by a first sending interface of the media conversion module, where the second packet includes the first AM, and the second packet is the first packet processed by the media conversion module, and calculating a time interval T1 between a time at which the media conversion module receives the first packet and a time at which the media conversion module sends the second packet, where the T1 is used to compensate for a first timestamp at which the first network device receives or sends the third packet.