Abstract: In order to realize the reliable detection of the primary user’s signal in low Signal-to-Noise Ratio, the paper presents a novel cooperative spectrum sensing algorithm based on cyclostationarity characteristics of the cyclostationary primary user’s signal. The algorithm adopts fully the different cyclic frequencies of the primary user’s signal and the sensing advantage of the cooperative detection technology to implement the cooperative spectrum sensing, overcomes multipath fading and shadowing effect of the wireless environment. The key of the algorithm is to detect the different cyclic frequencies of the primary user’s signal by the secondary users’ cooperative detection, and to make a final global decision according to the fusion data of the independent detection results of the secondary users’. Then a method is proposed in the paper to optimize the weight on basis of the deflection coefficient criterion to further improve the detection performance. The result of simulation shows that the algorithm proposed has better performance especially in low SNR.