A system information sending method is provided, to resolve a technical problem that UE may not receive a paging message when a DRX cycle is greater than an MP. A network device may separately set a modification period (namely, a first period) for first-type system information (which, for example, may include paging configuration information), to ensure that the first-type system information is not to be modified in the first period. For example, the first period may be greater than a DRX cycle. In this way, when a terminal device wakes up based on the DRX cycle, a time when the terminal device wakes up is still in the first period. The terminal device may normally receive a paging message indicating that the paging configuration information is to be modified, thereby obtaining new paging configuration information in time and avoiding missing a subsequent paging message.