Abstract: This study aimed to evaluate the quality characteristics of Shui ethnic red sour soup, using Miao ethnic red sour soup as a reference. The physicochemical components, free amino acids, and aroma compounds of Miao and Shui ethnic red sour soups were analyzed and compared using national standard methods, amino acid analysis, and headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that the contents of total acids, reducing sugars, fats, and proteins in Shui ethnic red sour soup were higher than those in Miao ethnic red sour soup. Nineteen free amino acids were detected in both types of red sour soup, and the content of savory amino acids in Shui ethnic red sour soup was twice that of Miao ethnic red sour soup. Proline and glutamic acid, with taste activity values (TAV) > 1, were identified as the key savory amino acids in both types of red sour soup. A total of 101 volatile compounds were detected in the red sour soups. Moreover, using orthogonal least squares-discriminant analysis (OPLS-DA) and variable importance in projection (VIP) selection, thirty-two key differential compounds, including hexadecanoic acid propyl ester, 4-ethyl-2-methoxyphenol, 5-cyclohexyl-2-pentanone, and sorbic acid, were identified in the red sour soups. Based on the relative odor activity value (ROAV), it was found that the sour taste was more pronounced in Miao ethnic red sour soup, while the fruity aroma was more prominent in Shui ethnic red sour soup. Both types of red sour soup contained salicyl methyl ether as the main contributor to the fatty aroma, but the volatile compounds responsible for the wine-like aroma differed. Ethanol was the main contributor in Miao ethnic red sour soup, while 4-ethylphenol was the main contributor in Shui ethnic red sour soup. In addition, sensory evaluation showed that Shui ethnic red sour soup received higher scores than Miao ethnic red sour soup. In conclusion, the Shui ethnic red sour soup exhibits superior quality and flavor, and has wider market development value.