A system message transmission method, comprising: determining, by a network side device, sets to which each of a plurality of system messages needing to be transmitted belongs, wherein the sets comprise a basic system message set and a specific system message set; determining, by the network side device, a transmission mode of the each of the plurality of system messages, wherein the transmission mode of all system messages in the basic system message set is a broadcast transmission mode, and transmission modes of all system messages in the specific system message set comprise a broadcast transmission mode, or a demand-based transmission mode, or a broadcast transmission mode and a demand-based transmission mode; and transmitting each of the plurality of system messages by the network side device according to the determined transmission mode, characterized in that, after determining, by the network side device, the transmission mode of the each of the plurality of system messages, the method further comprises: sending, by the network side device, a serial number or an identifier of a system message in the specific system message set to be transmitted using the broadcast transmission mode, or the demand-based transmission mode, or the broadcast transmission mode and the demand-based transmission mode, wherein sending, by the network side device, the serial number or the identifier of the system message in the specific system message set to be transmitted using the broadcast transmission mode, or the demand-based transmission mode, or the broadcast transmission mode and the demand-based transmission mode comprises: sending a system message in the basic system message set by the network side device, the system message in the basic system message set carrying an indication of the transmission mode of the system message in the specific system message set. determining, by a network side device, sets to which each of a plurality of system messages needing to be transmitted belongs, wherein the sets comprise a basic system message set and a specific system message set; determining, by the network side device, a transmission mode of the each of the plurality of system messages, wherein the transmission mode of all system messages in the basic system message set is a broadcast transmission mode, and transmission modes of all system messages in the specific system message set comprise a broadcast transmission mode, or a demand-based transmission mode, or a broadcast transmission mode and a demand-based transmission mode; and transmitting each of the plurality of system messages by the network side device according to the determined transmission mode, characterized in that, after determining, by the network side device, the transmission mode of the each of the plurality of system messages, the method further comprises: sending, by the network side device, a serial number or an identifier of a system message in the specific system message set to be transmitted using the broadcast transmission mode, or the demand-based transmission mode, or the broadcast transmission mode and the demand-based transmission mode, wherein sending, by the network side device, the serial number or the identifier of the system message in the specific system message set to be transmitted using the broadcast transmission mode, or the demand-based transmission mode, or the broadcast transmission mode and the demand-based transmission mode comprises: sending a system message in the basic system message set by the network side device, the system message in the basic system message set carrying an indication of the transmission mode of the system message in the specific system message set. sending, by the network side device, a serial number or an identifier of a system message in the specific system message set to be transmitted using the broadcast transmission mode, or the demand-based transmission mode, or the broadcast transmission mode and the demand-based transmission mode, wherein sending, by the network side device, the serial number or the identifier of the system message in the specific system message set to be transmitted using the broadcast transmission mode, or the demand-based transmission mode, or the broadcast transmission mode and the demand-based transmission mode comprises: sending a system message in the basic system message set by the network side device, the system message in the basic system message set carrying an indication of the transmission mode of the system message in the specific system message set.