Abstract: In this paper, light soy sauce was used as control, the characteristics of proximate indices, molecular weight distribution of protein / polypeptide, amino acid composition and sensory attributes of sweet soy sauce were studied using proximate indices analysis, sodium dodecyl sulfate- polyacrylamide gel electrophoresis, high performance liquid chromatography in combination with sensory evaluation. Results showed that the contents of Na Cl, total sugar, reducing sugar, salt- free solid and total acid in sweet soy sauce were 28%, 172%, 176%, 120%and 58% higher than those in light soy sauce, however its amino acid nitrogen was approximate 35% lower than the control.The proportion and the content of protein / polypeptide with high molecular weight in sweet soy sauce were remarkably higher than those in the control. The amino acid composition of sweet soy sauce was characterized by a large amount of sweet amino acids ( 45%) , followed by bitter amino acids and umami amino acids; however, the amino acid composition of the control was characterized by dominant umami amino acids ( 57%) , followed by bitter amino acids and sweet amino acids.Sensory evaluation indicated that sweet soy sauce processed prominent tastes of salty and sweet, and a harmonious mixture of umami, sour and bitter, etc.