Abstract: An approach based on the domain sample query is proposed in this paper to classify the web database.it obtains domain of the main attributes by analyzing descriptive attribute labels in the advanced query interfaces, the correllations of between web database with simple query interface and domain can be estimated by result schema and records of result pages, which obtained by submitting probing queries to simple query interface.The experiments on several domains have proved that this approach is effective and can achieve high classification precision, recall and F-measure values.