In view of the problem that marked the POI (Point of interest) of the current mobile users with no unified semantic ontology,this paper categorized POI and established POI ontology hierarchy tree for mobile users, then finished the mapping between the labeled POI information of users and the node of ontology tree by an improved mapping method to provided a unified standardized semantics for mobile users to mark information. An experiment is performed to evaluate the performance of the new similarity measure by using the labeled information of users in a period of 5 weeks, the results show that the method has high accuracy.