An upstream resource grant method, a device, a passive optical network, and a computer-readable storage medium are provided. The upstream resource grant method includes: obtaining, by an optical line terminal, an upstream grant message on which transformation processing has been performed, wherein a transformation parameter used for the transformation processing includes a physical identity of an optical network unit (ONU); and sending, by the optical line terminal, the upstream grant message on which the transformation processing has been performed, wherein the upstream grant message carries an upstream resource grant indication of the optical network unit, and the upstream resource grant indication indicates an upstream resource granted to the optical network unit. According to this application, an occurrence probability of a rogue ONU phenomenon is reduced, thereby improving service running stability of a PON system.