Protégé is one of the most popular tools of the ontology visualization. The “Protégé” tools are being applied for further development in various disciplines for better understanding of knowledge. These tools commonly use four methods of ontology visualization, namely, indented list, node-link and tree, zoomable, and focus+context. The purpose of this work is to present a study on application of these four methods in the development of different kinds of protégé visualization tools and categorize their characteristics and features so that it assists in method selection and promotes further future research in the area of ontology visualization.