In this study， Gas chromatography-mass spectrometry (GC-MS) was used to analyze the changes of flavor substances during the fermentation of congee， and its physicochemical properties and sensory quality were analyzed. The results showed that the 0-48 h pH value rapidly decreased from 4.09 to 4.13 during the fermentation process， and the acidity showed a step rising trend. The acidity increased from 4°T to 31.2°T during 0-48 h fermentation. The total sugar content increased first and then decreased， and the total sugar content increased from 85 mg/L to 93 mg/L during 0-6 h fermentation. The total sugar content decreased from 83 mg/L to 52 mg/L during fermentation 12-48 h. With the extension of fermentation time， L value of congee showed a decreasing trend from 57.5 to 30.55 for 0-48 h， a value and b value increased from 0.55 to 0.35 for 0-48 h， and b value increased from 0.35 to 5.70. A total of 16 amino acids were detected from the congee samples. The content of total amino acids increased to twice of that of 0 h after fermentation for 48 h， and the content of glutamic acid and aspartic acid was the highest. The detection results of electronic nose technology showed that W5S (nitrogen oxide compounds)， W1S (methyl groups) and W1W (sulfide sensitive) sensors were more responsive to congee samples. In terms of taste， sour porridge has the strongest response signal of sour， sweet and salty taste. GC-MS analysis showed that 90 volatile compounds were detected from the sour porridge， among which ethyl acetate， eunesol， nonylaldehyde， ethyl enanthate and acetic acid were important aroma components. This study provides theoretical reference for further development of congee products.