Abstract-Indoor navigation will become an important application on a smartphone for Location-Based Service (LBS). An indoor navigation system should work under normal circumstances and during emergencies, such as fires, during a building power shut down, alarm, etc. The LBS should be able to help users find the best exit route to the outside of the building under all circumstances and with high reliability. In this research, we develop an indoor ontology model for indoor navigation. This ontology model defines the indoor environment attributes such as location nodes, and connection points. The location nodes with the location information allow navigation in the indoor environment. Connection points are able to separate the map zones and the building floors into a "Map sheet." This ontology approach allows the LBS works in both normal circumstances and emergencies. This model provides a reliable indoor navigation system for LBS.