Abstract: Based on the matter-element,extension set and correlation function etc.in extension theory,the matter-element extension model for overall assessment of soil corrosivity for gas pipeline is set up.This paper introduces method and procedure to determine the matter-element assessment,classical field and segment field,assessment-ready matter-element,correlation function,weight,assessment-ready matter element overall correlation degree and assessment degree.The 23 km-long high-pressure gas pipeline of Changzhou-Ganghua was studied where salt content,water content,spontaneous potential,redox potential and resistivity were chosen as the evaluation indexes.The abovementioned model was utilized to evaluate the soil along the investigated pipeline,and the soil corrosivity was recognized as IV degree from the point views of overall correlation degree and variable eigenvalue.Strict corrosion-proof work and regular NDTs will be mandatory if the gas pipeline passed through the soil with higher corrosivity.The study shows that the matter-element extension model is adaptable for overall assessment of soil corrosivity for gas pipeline.However,deeper investigation and discussion are desired on appropriate assessment standard,evaluation index selection,correlation function and weight calculation.