Space-time block codes (STBCs) play an important role in spatial diversity technologies.The Alamouti scheme provides full diversity, full rate and needs simple separating decoding but is for only two antennas.For more than two antennas, qtasi-orthogonal space-time block codes (QOSTBCs) are able to provide full rate but enjoy only a partial diversity and need pairwise decoding.The recently proposed constellation-rotated QOSTBCs (CR-QOSTBCs) can achieve both full diversity and full rate.In this paper, we propose a novel transmit diversity scheme based on CR-QOSTBC and multi-carrier code division multiple access (MC-CDMA), using four transmit antennas and one receive antenna, which not only provides full diversity and full rate but also uses simple decoding, achieves good performance in frequency selective fading channels due to the ability of diversities in space, time, frequency and coding.The simulation is then complimented to show that the bit error rate (I3ER) performance of CR-QOSTBC-MC-CDMA to is improved distinctly.