Topic Maps (TM) are standardized by ISO 13250 for the pur¬pose of semantic annotation of WWW resources. This paper presents the knowledge navigation system for E-Government information portal based on Topic Maps technology, including four layers: information resources layer, knowledge layer, information navigation server layer and application layer. The method of constructing topic maps from domain ontology is discussed. The knowledge layer is abstracted from large quantities of distributing heterogeneous municipal information resources by using TM. Navigation scope is built on the knowledge level which enlarges the navigation unit granularity and quantity of receiving information, shortens the navigation routing, improves the efficiency of navigation, and achieves the intelligent information retrieval. The research is valuable in E-Government and knowledge navigation.