Spectrum sensing is a key technology in Cognitive Radio (CR). It is an important function to be performed by every cognitive radio. Either single or multiple users can take part in spectrum sensing process. This paper presents a multiple thresholds cooperative spectrum sensing algorithm based on signal-to-noise ratio (SNR). In the first phase, the cognitive nodes that satisfy the request of double thresholds apply the cooperative sensing. In the second phase, the nodes that in the doubt-window participate in cooperation according to the SNR threshold, if there is no final decision by the fusion center in first phase. The fusion center combines the detection results by weighting factor which is calculated by the SNR. Simulation results show that the proposed scheme could improve the system performance. And the proposed scheme is more suitable in the environment of medium to low SNRs.