A system information obtaining and sending method and a related apparatus are disclosed. A terminal receives configuration indication information sent by a network device, where the configuration indication information includes RACH preamble configuration information corresponding to first system information; and the terminal sends a first request message used to obtain the first system information, to the network device according to the RACH preamble configuration information corresponding to the first system information, so that the RACH preamble configuration information is reused in the first request message.