The bandwidth of spectrum sensing can be enlarged in software radio pla tform by using multi-step frequency domain energy detection. Nevertheless, the energy detection is sensitive to noise uncertainty, and signal sample autocorrelation method is robust to it. To improve the detection performance of software radio, a step-by-step wideband spectrum sensing method based on signal sample autocorrelation is proposed. Firstly, the principle of signal sample autocorrelation and a step-by-step wideband spectrum sensing procedure based on it are described.Then, the whole procedure for wideband spectrum sensing using MATLAB is simulated. The simulation results demonstrate that our proposed method can achieve the required detection performance under different signal-noise ratio (SNR). In addition, to balance the bandwidth resolution and the detection speed, we further propose to apply variable step values in two stages of wideband spectrum sending based on signal sample autocorrelation detection, which can obtain higher detection resolution of the frequency bandwidth and shorter detection time.