A Pre-processing Least Squares Constant Modulus blind multiuser detection Algorithm based on Decision-Feedback (PDF-LSCMA) in antenna array system is proposed in this paper.It pre-processes the received signals from the antenna array and utilizes the least squares constant modulus algorithm based on decision feedback to detect the DS-CDMA signals.This algorithm can ensure the convergence to the expected signal and enhance the performance of the system.The robustness of PDF-LSCMA to the DOA estimation error and the maximum value of DOA estimation error are also analyzed in this paper.Simulation validates the algorithm and theoretical analysis.