This application provides a system message transmission method, an apparatus, and a system. A first communications device configures a MIB message, and the MIB message may carry various different information used to transmit a SIB1, for example, any one or more of scheduling information, first information, and an operation mode of a carrier, so that a second communications device receives the SIB1 based on the MIB message. The first communications device may flexibly configure information used to transmit the SIB1. In addition, when configuring the MIB message, the first communications device may consider ensuring, through configuration or implicit indication, that resource locations for transmitting SIB1s of different cells in one period are different. This type of interference isolation mechanism can avoid mutual interference between transmission of SIB1s of different cells, so that transmission reliability of the SIB1s can be improved.