Abstract: Searching for the desired images similar to a query picture is very time-consuming in an image database system. To speed up the search process, a signature file containing the signatures associated with database images is frequently used as a filter to prune off non-promising images at the early stage of query processing. In this paper, we propose a novel structure for organizing signatures. By using this new indexing structure, the number of signatures to be examined per query is reduced significantly. In particular, the reduction ratio in examining signatures is about 51% as compared to the quick filter. As a result, image retrieval in image database systems becomes very efficient by using our method.