Embodiments of the present disclosure disclose a method for transmitting system information, a base station and a terminal, the method including: receiving, by a base station, MSG1 transmitted by a terminal; determining an access purpose of the terminal according to a preset mapping relationship between a physical random access channel resource used by the terminal to transmit the MSG1 and the access purpose of the terminal, the access purpose including requesting the system information, requesting initial access, or requesting the system information and the initial access at one time; transmitting, by the base station, MSG2 to the terminal if the access purpose of the terminal is to request the system information, or to request the system information and the initial access at one time. It is possible to transmit the system information according to the requirements of the terminal, which is beneficial to optimize the system efficiency.