The risk factors of a city gas pipeline were indentified and studied with Kent score method to set up an index system for the risk assessment of the pipeline.The traditional extenics assessment has been extended to adjust the procedure for assessing the range elements

correlation

and rating

which is called the multi-level extenics assessment method;the corresponding guidelines have been set up for the multi-level integrated assessment of city gas pipelines.The risk grades of different sub-indexes of a city gas pipeline can be evaluated through the multi-level extenics assessment to determine the risk grade of the overall system.A gas pipeline in Handan city was taken for an example to demonstrate how to obtain the risk grades at different levels for the risk evaluation of city gas pipelines.Finally

the reliability of the method proposed in this paper has been validated through comparative analyses of real data.