Abstract: To improve the spectrum sensing performance, firstly using the characteristics of power spectral function and the concept of Rayleigh entropy, the spectrum sensing algorithm based on power spectral are theoretically analyzed and an algorithm of spectrum sensing based on the difference between the maximum value and minimum value of the power spectral is put forward. And then the detection threshold and the detection probability are derived. Finally the simulation results are given. Theoretical analysis and simulation results show that in AWGN channel and Rayleigh fading channel the algorithm has good detection performance, and it is better than the existing spectrum sensing algorithm using power spectral. The algorithm does not need the primary user information and complex eigenvalue decomposition. The decision threshold can be given accurately when the false probability is fixed .