Abstract: Without the priori information of interference system, iterative detection algorithm based on minimum- error-rate threshold can make a good performance. In practice, however, accurate noise estimation is difficult to achieve because of low SNR, which results in a large deviation between the iterative convergence threshold and the minimum-error-rate threshold, and then causes a deterioration in detection performance. To address these issues, an improved iterative detection algorithm is proposed in this paper. Meanwhile, the iterative estimation expression of noise power, signal power and signal occupancy rate are given by detailed derivation. In addition, the constrained relationship between detection performance and SNR is discussed, and the closed-form expression of the minimum SNR is proposed to meet certain performance indicators. The simulation results show the effectiveness of the proposed algorithm.