1. A method of symbol detection for multi-input multi-output dual-signaling uplink CDMA systems that adopts dual-signaling at the transmission end for flexible switching between transmission diversity and being spatially multiplexed based on the variations of space-time channel conditions, characterized by: based on the channel characteristics, each user's data stream can be either orthogonal space-time block encoded (O-STBC) for transmission diversity or spatially multiplexed (V-BLAST) for high spectral efficiency.