A reverse data transmission apparatus and method in a mobile communication system. A mobile station receives information about an MADR (Maximum Allowable Data Rate) from a base station in a first predetermined frame period, determines a data rate equal to or lower than the MADR, and requests the determined data rate to the base station. If an MADR received from the base station in a second frame period following the first frame period is higher than the requested data rate, the mobile station starts data transmission. Then, the mobile station measures a traffic to pilot ratio (T/P) from the base station and controls the data rate according to the T/P during data transmission.