This application provides an uplink access method and a device. The method includes: a network device receiving indication information sent by a terminal device when the terminal device goes online, where the indication information is used to trigger the network device to send uplink registration window indication information on a first port; the uplink registration window indication information indicates a registration window location at which the terminal device sends uplink registration information; and the network device sends the uplink registration window indication information on the first port according to the indication information. According to the technical solutions provided in embodiments of this application, in a P2MP working mode, a network device may be prevented from periodically indicating a registration window, thereby reducing resource overhead and power consumption.