An improved scheme with cooperative diversity based on distributed space-time block coding (WCD-DSTBC) is proposed, which effectively achieves diversity gains and improves the performance of the system by sharing some single-antenna users' antennas to form a virtual antenna array and combining with distributed spacetime block coding (DSTBC) mode. Then the relation between the system BER and the interuser BER for WCD-DSTBC scheme is theoretically derived and the closed-form expression of BER for WCD-DSTBC system is obtained. The simulation results show that the proposed WCD-DSTBC achieves distinct gains over the non-cooperative multi-carrier CDMA (MC-CDMA) system. When system BER is 1e−3 and interuser BER is 1e−3, about 2.5 dB gain can be gotten. When interuser channel state information (CSI) outgoes the users' individual CSI, about 3 dB gain is also achieved.