Disclosed is a method for decoding received signals on communication channels between at least one transmit antenna and plural receive antennas in a space-time coded direct sequence (DS)-CDMA communication system. The decoding method includes steps of: adjusting the step-size which is an update unit for the tap weight vector for despreading received signals; updating the tap weight vector using the step-size; and despreading the received signals using the tap weight vector. According to the decoding method, the optimal performance can be achieved because the tap weight vector and the step-size are adaptively updated according to changes of communication environment. Such superior performance is more remarkable as the number of receive antennas and transmit antennas increases.