Abstract: In order to address the problem of spectrum sensing with the random presence of authorized users in cognitive radios, a double threshold based multi-user cooperative spectrum sensing method is proposed. This method first makes local decisions based on double threshold. If the test statistic is larger than the high threshold then decision 1 is made, otherwise decision 0 is made. If the test statistic is between the high threshold and the low threshold, then the test statistic is sent to the fusion center directly. The fusion center combines the direct test statistics by equal gain combination scheme and then makes a hard combination scheme based on rule by using all the results. Simulation shows shat the proposed method is superior to the "OR-rule" hard combination scheme and is only a little inferior to the equal gain combination scheme (EGC) but the proposed method can save a lot of transmitted bits in the network.