Abstract: Considering the error propagation effect and high complexity of vertical bell labs layered space time codes，a novel nonlinear module algebra precoding algorithm based on QR decomposition for VBLAST in multi-user MIMO-MC-CDMA downlink system is proposed，QR decomposition is used for precoding matrix，the nonlinear module algebra THP precoding is used between sub-carrier channels of MC-CDMA to eliminate interference from other signals at the transmitter，and can eliminate the error propagation effect of layered space-time codes effectively.At the receiver，ZF and MMSE criterion are used for detection，and the complexity of the downlink receiver can be reduced.Simulation results show that the proposed algorithm is better than the traditional algorithms in the system BER performance.