A method determines the data rate of traffic data to be transmitted from a mobile station to a base station in a mobile communication system, by considering a delay time required for the generation and transfer of data rate control information. The method includes steps of transmitting control information to the base station, the control information corresponding to the traffic data of an ith frame, the ith frame having a predetermined data rate; receiving, in response to the transmitted control information, data rate control information from the base station, the data rate control information including an instruction; and determining a maximum data rate of the traffic data to be transmitted during a next frame, by applying the instruction of the data rate control information to the predetermined data rate of the ith frame.