A method, apparatus, and system for data transmission, wherein the method comprises: the network-side network element determining the target data transmission mode; the network-side network element sending instruction information to the terminal through the base station transmission in order to instruct the terminal to switch to the target data transmission mode with which to implement data transmission; wherein, the target data transmission mode is NarrowBand IoT (NB-IoT) data transmission or Long-Term Evolution (LTE) data transmission.