The present invention relating to the mobile communication filed discloses a transmitting method and system in the universal mobile communication system to improve the multipath interference resisting ability of the MIMO downlink physics channel on the premise of having the compatibility of UMTS system. In the present invention, each branch signals of the MIMO downlink physics channel at the network side compose the single-carrier symbols with cyclic prefix; then the symbols are sent to the UE side through the emitting antennas corresponding to the branches after being combined with the signals of other physics channel; UE processes the signals of the downlink physics channel using MIMO that has been received by the antenna in a frequency domain multi-user detecting mode, while a common CDMA receiving method is retained to other downlink physics channel.