One example transmission method includes receiving, by a network device, a first transmission parameter that is sent by a server and that is used to transmit assistance data, where the first transmission parameter includes configuration information and/or priority information, and the configuration information is used to indicate a transmission cycle of each of one or more system messages and/or a size of a data volume that can be carried in each of the one or more system messages, and sending, by the network device, first configuration information to the server according to the first transmission parameter, where the first configuration information is used to indicate a transmission cycle of a first system message and a size of a data volume that can be carried in the first system message, and the one or more system messages include the first system message.