Abstract: Yulin-Jinan Natural Gas Pipeline is currently in the danger of pipeline leak and its secondary disasters, so an integrated leak detection scheme is needed to ensure its safe operation. In view of the lack of trunk line measurement and numerous pressure measuring points along large-scale complex natural gas pipeline systems, the pressure distribution leak detection system based on on-line simulation developed by a domestic company was adopted to carry out the real-time leakage detection on the whole pipeline, monitor the running state of the pipeline system continuously and identify possible minor leaks and locate them in time by conducting comparative analysis on on-line simulation pressure and measured pressure deviation distribution. The results show that this leak detection system can not only be used to realize the leak detection of large-scale complex natural gas pipeline systems, but also identify abnormal events, e.g. instrumentation faults and station operation. What's more, it breaks through the limitation of sectional leak detection of pipeline system, provides the dynamic monitoring and location on natural gas pipeline leak.