The key problem in unstructured P2P system is how to control "Flood". Some studies focus on constructing more efficient topology while others focus on better query algorithms. This paper presents HICUS (Hierarchical Interest-driven Community-based Unstructured System) motivated by a basic thought-whether the resources correlate with topology distinguishes structured and unstructured P2P essentially. By introducing hierarchical "interest", HICUS organizes a quasi-structured topology through a pure distributed way, and provides a new platform for query algorithms. We study the procedure and performance of topology organization, and the simulations show that HICUS forms a small-world which can significantly improve the routing efficiency.