Embodiments of this application provide an upstream resource grant method, a device, a passive optical network, and a computer-readable storage medium. The upstream resource grant method includes: An optical line terminal obtains an upstream grant message on which transformation processing has been performed, where a transformation parameter used for the transformation processing includes a physical identity of an optical network unit (ONU); and the optical line terminal sends the upstream grant message on which the transformation processing has been performed, where the upstream grant message carries an upstream resource grant indication of the optical network unit, and the upstream resource grant indication is used to indicate an upstream resource granted to the optical network unit. The technical solutions provided in the embodiments of this application help reduce an occurrence probability of a rogue ONU phenomenon, and further improve service running stability of a PON system.