Embodiments of the present disclosure provide a data transmission method, apparatus and system. The method includes: receiving an RTS frame sent by a legacy STA on a channel including a primary channel, and sending an indicating frame to the legacy STA and a new station, for enabling the legacy STA to send data on the channel including the primary channel according to the indicating frame, and enabling the new station to send data on a secondary channel not occupied by the legacy STA according to the indicating frame. By adopting the data transmission method, apparatus and system provided by the embodiments of the present disclosure, uplink OFDMA data transmission under a compatible mode is achieved, and the problem of bandwidth waste caused by data transmission of the legacy STA is solved.