Result size estimation of value predication in XML query is a multiple attributes dependent problem. It is different from the counterpart in relational database, for the multiple attributes in XML involve not only the value data, but also the structural information. To solve the problem, this paper proposes a wavelet-based histogram for the result size estimation of value predication in XML query. It also gives the way to identify the multi-dimensional dependent element set, to rewrite the value predication and value denotation of structural information. Experimental results show that the algorithm achieves on accurate result size estimation for value predication in XML query.