An improved decision tree method for web information retrieval with self-mapping attributes is proposed. The self-mapping tree has a value of self-mapping attribute in its internal node, and information based on dissimilarity between a pair of mapping sequences. This method selects self-mapping which exists between data by exhaustive search based on relation and attribute information. Experimental results confirm that the improved method constructs comprehensive and accurate decision tree. Moreover, an example shows that the selfmapping decision tree is promising for data mining and knowledge discovery.