Abstract: The orientational filter is an integral part of content-based image retrieval, which is now mainly applicable to general image field instead of particular image field. Statistical method and fuzzy set theory are introduced in the clustering analysis which is made for the subsets of the particular image field in each and all directions. The degree of membership is computed according to the results of clustering analysis and used as the weight of the texture characteristic vector in a certain direction, and k dominant directions are determined correspondingly according to the degree of membership. Texture characteristics are thus computed from the k dominant directions and used to form texture characteristic vector. Similarity measure between texture characteristic vectors is computed by means of Euclidean distance. Experiments showed that the texture characteristic vector obtained from π, π/2, 0, 3/2π directions is better than that obtained from the computation of 0, π/4, π/2 and 3/4π in matching precision. Moreover, such an orientational filter is applicable to particular image field.