A method and an apparatus for transmitting system information and a method and an apparatus for receiving system information are provided. The method includes: acquiring, by a base station, a preset modification period of enhanced system information, where the enhanced system information is system information on which enhanced transmission needs to be performed; the modification period of the enhanced system information is an integer multiple of a modification period of non-enhanced system information; and the non-enhanced system information is system information that is transmitted, based on scheduling by using a control channel, in a system information window; and transmitting the enhanced system information in an enhanced transmission manner in the modification period of the enhanced system information according to a configured time-sequence location. According to the methods or the apparatuses in the present invention, occupied transmission resources can be reduced.