Following some rules, the Cognitive Radio Networks (CRNs) can be divided into several clusters, each cluster has a Common Control Channel (CCC) to exchange control information. The cluster-based CCC is one of the solutions to the problem of spectrum sharing on MAC protocol for CRNs. In order to validate the clustering structure, we propose a MAC protocol based on clustering. In our protocol, channel access time is divided into a sequence of superframes. Each period in superframes is corresponding to the operation of cluster node. This mechanism can make the cluster structure more robust to the primary users' activities. Simulation results reveal that our proposed MAC protocol can achieve higher throughput and lower delay in high traffic conditions.