Abstract: In the two-tier network constituted by femtocell and macrocell, predecessors put forward using the cognitive radio technology to solve the problem of interference existing in the network. However, most studies just focus on the management of spectrum resources, and have not provided efficient spectrum detection methods. A two-tier cooperative spectrum sensing is prosposed based on double thresholds combined with the spectrum sensing technology in cognitive radio. By allocating the empty spectrum resources to the femtocell users, the proposed algorithm improves the utilization of spectrum resources, and suppresses the interference between femtocell and macrocell effectively. For the femtocell users, this paper derives the detection probability and false alarm probability of two-tier spectrum sensing based on double thresholds. A two-bit-coding fusion rule of sensing information is proposed for the femtocell network. At the same time, the specific implementation steps are given for the two-tier cooperative spectrum sensing based on double thresholds. Simulation results show that the proposed algorithm can effectively improve the detection probability of single femtocell user. It also shows that the two-bit-coding of the sensing information and the encoded information fusion in the center can effectively improve the detection performance and anti acoustic performance of the system.