At present, Minimization of Pattern Tree Queries, becomes the key factor that affects query processing performance of XML data. An improved algorithm is proposed with structural index of XML, based on analyzing the existing methods of Minimization of Pattern Tree Queries. It's effective to solve that grammar level optimization can't effectively remove redundant nodes of the defect in the common sense, so as to improve the efficiency of the inquiry. Experimental results show the effectiveness and accuracy of the proposed minimization algorithm.