Management of natural gas pipeline is an important task for economical and safety operation, loss prevention and environmental protection from methane emission. A leak detection of gas pipeline, therefore, plays a key role in the overall integrity management for a pipeline system. Especially for a long pipeline operated alongside of densely populated areas, a leak detection system is an indispensable condition to allow its construction. In this paper, a leak detection method based on a dynamic simulation with wave equations is presented. An industrial application to one of the longest gas pipeline is also presented with its performance information.