A data communications method, apparatus, and system are provided. The method includes: sending an association request message to an access point; receiving an association response message sent by the access point, where the association response message includes an association identifier; generating a data frame, where a format of the data frame is a simplified frame format, and a frame header of the data frame includes a source address and a destination address, where the length of the source address is shorter than the length of a Media Access Control (MAC) address, and the source address includes the association identifier, the association identifier and a multicast unicast indicator, the association identifier and a data type, or the association identifier, the data type, and the multicast unicast indicator; and sending the data frame to the access point.