Abstract: A low-complexity signal detection approach based on Kaczmarz algorithm is proposed to iteratively realize MMSE detection for uplink massive MIMO systems. By applying an equivalent augmented matrix in MMSE detection, the proposed algorithm avoid the exact matrix inversion and Gram matrix computation. Moreover, promising initial estimation and an approximate method to compute soft-output information is utilized to further reduce the complexity. Simulation results demonstrate that the proposed approach outperforms recently proposed algorithms in complexity and performance. Meanwhile, the FPGA implementation results verify that our proposed method can efficiently compute the approximate inverse with low complexity.