A Radio Network Controller (RNC) in a high speed wireless communication system includes an apparatus to perform method for changing a serving cell in the high speed wireless communication system. The RNC receives UpLink (UL) cell change determination information representing UL channel states from a serving Base Station (BS) and a target BS. The UL is received if a UL soft handover of a Mobile Station (MS) is initiated depending on a DownLink (DL) channel quality of the MS. The RNC can determine UL cell change timing of the MS using the UL cell change determination information. Thereafter, the RNC can send an instruction of a UL cell change of the MS to the serving BS and the target BS.