A space-frequency joint blind multi-user adaptive detection algorithm in smart antenna MC-CDMA system is proposed in this paper. It combines the receiving beam-forming in space-domain with combinational detection in frequency-domain and optimizes the detector simultaneously in two dimensions. It can enhance the performance of detection of the system. The bit error probability of the proposed algorithm is also analyzed in this paper. The proposed algorithm is simulated and compared with the two-step algorithm in which the adaptive beam-forming is used first and then the combination in frequency-domain is carried out. Simulation results show that the proposed algorithm is superior to the latter.