In cognitive radio networks,in order to improve the security performa nce and sensing efficiency,a secure spectrum sensing algorithm based on blockch ain technology is proposed.The algorithm first evaluates the reliability of the sensing node,and obtains the initial trust value of the node through the evalu ation algorithm.Based on the initial trust value,the fusion center will update the trust value of the node regularly according to the change of the environmen t.The updated trust value is stored in the management center of the blockchain. The management center of the blockchain encrypts the node information,and a no de and its own trust value form a one-to-one mapping.When cognitive radio net wo rks perform spectrum sensing,the fusion center selects a limited number of node s with high trust value to participate in cooperative sensing,which can improve the accuracy of sensing,reduce the energy cost and enhance the robustness of c ognitive radio networks.Simulation results show that the performance of the pro posed algorithm is much better than that of the traditional algorithm.Under the same experimental conditions,the sensing accuracy is improved by 5%,and the e nergy consumption is reduced by 12%,which greatly enhances the robustness of co gnitive network and the security of spectrum sensing.