Abstract: To reduce the co-tier interference among femtocell base stations (FBSs) in ultra-dense networks (UDN), an interference-limited clustering and resource allocation (ILCRA) scheme is proposed, in which preset threshold is used to limit the number of FBS in each FBS cluster. Firstly, FBSs are divided into clusters, and the sum weights of interference in each FBS cluster can not exceed the preset threshold. Secondly, user equipment (UE) is clustered by exhaustive graph coloring algorithm in each FBS cluster. Then, the resources are allocated independently within each FBS cluster. Sub-channels are assigned according to the throughput of UE clusters on each sub-channel. Finally, the water-filling algorithm is performed to allocate power to UEs in each FBS cluster. The simulation results show that the proposed scheme effectively limits the number of FBS in each FBS cluster and improves system throughput and spectrum efficiency.