Abstract: Red sour soup was used as the research object in the study. Sensory evaluation, electronic nose and gas chromatography-ion mobility spectroscopy (GC-IMS) were used to analyze the difference of flavor between serious, slight and normal samples. The results showed that there were significant differences among the three kinds of red sour soup by sensory evaluation, principal components and linear discriminant analysis of electronic nose, and urn odor was the main reason for the differences. A total of 64 flavor components were detected and identified in three sour soups. The identified compounds include 9 components such as acids (6), alcohols (14), aldehydes (8), esters (19), ketones (8), pyrazines (3), monoterpenes (2), ethers (2), sulfides (2). Among them, the ion peak volume of butyric acid, valeric acid, 2-methylpropionic acid, hexanal and benzaldehyde were 20515.80, 1860.73, 2413.18, 6274.68 and 668.61 respectively in the urn odor sample (Y1), which were significantly different from the other two soup samples (Y2 and Y3) and which might be the cause of the flavor difference between the urn odor sample and other sour soup samples.