Abstract: In the case of large-scale antennas, there are high complexity problems in the existing zero forcing successive interference cancellation (ZF-SIC) algorithm and the minimum mean square error successive interference cancellation (MMSE-SIC) algorithm. In order to solve this problem, low complexity ND-ZF-SIC algorithm and ND-MMSE-SIC algorithm are proposed. First, the diagonal matrix decomposition is used to decompose the large matrix into the sum of the diagonal matrix and the hollow matrix. Secondly, the Neumann series approximation is used to convert the direct inversion of the large matrix into the sum of the products of the diagonal matrix inversion. In order to reduce the complexity while ensuring the accuracy of the approximation, the first two terms of the Neumann series are taken. Since the inverse of the diagonal matrix only requires the reciprocal of the elements on the diagonal, ND-ZF-SIC and ND-MMSE-SIC greatly reduce the complexity of the original algorithm. The simulation results of ZF-SIC, ND-ZF-SIC, MMSE-SIC and ND-MMSE-SIC show that the error bit performance of ND-ZF-SIC and ND-MMSE-SIC is similar to ZF-SIC and MMSE-SIC, respectively.