With the rapid development of urbanization，a variety of accidents，environmental disasters can happen at any time，in all of them，the greatest threat to the city is the safety and the reliability of the urban lifeline system，and the urban underground pipe network in urban lifeline system is the important part，whose safety affects the normal operation of the city，the safety of people’s lives and property. The research project of the risk assessment method of urban underground pipeline network establishes the urban gas pipeline network risk assessment model and gets the level of risk distribution network matrix，develops the urban gas pipeline network risk analysis and assessment，early warning and management capabilities of city gas pipeline network risk assessment supporting software through the investigation of the present situation of urban underground pipe network and data collection，exploring the failure factors of underground pipelines in the complex urban environment，calculating its weight，selecting the fuzzy comprehensive evaluation method，and then obtains the reliability and applicability of the model and systems by the practical application of the project. By studying this project，we can build a comprehensive platform of risk assessment and dynamic early warning system，the safe operation and the level of integrity of the city buried gas pipe network has been greatly improved，the security of the city gas pipeline network can be improved effectively，and it has good economic and social benefits.