The 'Collaborative Tagging' is gaining popularity on Web 2.0, this new generation of Web which makes user reader/writer. The 'Tagging' is a means for users to express themselves freely through additions of label called 'Tags' to shared resources. One of the problems encountered in current tagging systems is to define the most appropriate tag for a resource. Tags are typically listed in order of popularity, as del-icio-us. But the popularity of the tag does not always reflect its importance and representativeness for the resource to which it is associated. Starting from the assumptions that the same tag for a resource can take different meanings for different users, and a tag from a knowledgeable user would be more important than a tag from a novice user, we propose an approach for weighting resource tags based on user profile. For this we define a user model for its integration in calculating the weight of a tag and a formula for calculating it based on three factors namely the user, the degree of approximation between its centers interest and the field of resource, expertise and personal assessment for tags associated to the resource. A resource descriptor containing the best tags is created.