Abstract: An Adaptive Threshold Option-Improved Stagewise Orthogonal Matching Pursuit (ATO- IStOMP) algorithm is proposed to solve the problems that wideband compressed spectrum sensing reconstruction algorithm is not ideal under the condition of unknown sparsity. According to the distribution characteristics of iterative residuals, the algorithm adaptively adjusts the threshold of the atomic selection decision, so that each iteration can select multiple atoms efficiently as a candidate set, At the same time, this algorithm modifies the iterative termination condition by using the residual ratio threshold, which can stop the iteration without knowing sparsity and enhance the robustness of the algorithm in low signal-to-noise ratio. The simulation results show that the ATO-IStOMP algorithm can realize the blind reconstruction of the original signal and the reconstruction performance is good under the low SNR environment.