This paper presents OntoRT, an ontology model for Role-base Trust-management(RT) framework, which covers a large fragment of RT including RT0, RT1, RT2 and application domain specification documents (ADSDs). RT addresses distributed authorization problems in decentralized collaborative systems. OntoRT establishes a common vocabulary for RT roles and policies across domains. We describe OntoRT formally in Description Logic(DL) SHOIN(D) and DL-safe SWRL rules. Basing on our logical formalization it is feasible to authorize and analyze RT policies automatically via the state of arts DL reasoners. Finally, we show how OntoRT can be integrated with OWL-DL ontologies which are W3C standard for representing information on the Web. By referring to OWL-DL ontologies that provide rich domain knowledge, specification and management of RT policies are simplified.