Abstract: In the XML query algorithm based on matching pretreatment，three important existing tree matching models are used and the matching results of data sets are presented according to the matching cost in a descending order.The function of matching pretreatment is added to improve the existing algorithm，and a series of experiments are conducted.The results show that this algorithm can remove the unwanted nodes in the tree and promote the efficiency of data sets retrieval when the data scale is very large.Especially the recall rate，the rates of accurate survey and the average response time are satisfying.This algorithm is applied in the unity retrieval system of scientific and technological resources database.It can facilitate the navigation of resources，narrow the search scope and promote the efficiency of this system.