Abstract: Based on the study of rough sets,combined with the Nearest ordinary set of a fuzzy set and the Farthest ordinary set of a fuzzy set and by the help of lp(A,B)、D(A,B) and membership of rough set, a new measure of fuzziness in rough sets is introduced, some characterizations of this measure are given and proved. This new measure presented in this paper is very important in theory and in practice.