Abstract: Owing to the influence of unknown carrier offset and noise uncertainty, the maximum value and the minimum value of signal’s power spectral were unable to be evaluated by frequency single point. The spectrum sensing algorithm using the ratio of average value of maximum and minimum power spectral was proposed. This algorithm was specifically designed as follows. Firstly, the maximum value was estimated by the power spectral average of neighboring points to the base frequency, and the minimum value was estimated by the power spectral average of neighboring points to the midpoint frequency. Secondly, the ratio of the maximum and the minimum value was used as the detection statistics. Finally, the algorithm’s false alarm probability and a detection threshold were deducted. The simulation results in Additive White Gaussian Noise channel and Rayleigh fading channel show that the proposed algorithm is better than the PSC、PSRA algorithm, and the influence of the unknown carrier offset and noise uncertainty on the algorithm is reduced.