Disclosed is a method and apparatus for providing uplink packet data services through an E-DCH in an asynchronous WCDMA system. A transport block size (TBS) for transmitting uplink transport channel data is determined. A combination of a spreading factor and a modulation scheme for uplink channel data transmission, corresponding to the determined TBS, is selected according to transmittable physical channel data bit sizes and puncturing limit values. The TBS is transmitted by incorporating it into control information of the uplink transport channel data. The modulation scheme and spreading factor combination is determined based on a physical channel data bit size that maximizes transmission efficiency and minimizes the number of punctured bits, without requiring an additional physical channel in transmitting the uplink data having the TBS. This method maximizes uplink transmission efficiency to save transmission resources and reduces signaling overhead required to transmit E-DCH control information.