Abstract: In the present study, the single fruit weight, soluble solids, titratable acid content, sugar and organic acid composition and content of seven mulberry varieties were identified and determined at three development stages. The results showed that the contents of soluble solids and suger increased during the development of mullberry fruit, while the organic acid decreased. Eight kinds of organic acids, including citric acid, malic acid, quinic acid, succinic acid, tartaric acid, ketoglutarate, ascorbic acid and oxalic acid, were detected and determined. Citric acid was the most abudant organic acid, followed by quinic acid and malic acid. The relative content of citric acid ranged from 44.84% to 80.86%. Fructose and glucose were most important suger content. The content of Fructose and glucose reached to 57.79 mg/g and 66.72 mg/g respectively in Taiwan Changguosang at last development stage. And sucrose was only detected in Taiwan Changguosang.Through correlation analysis, titratable acid was negatively correlated with soluble solids, fructose, glucose and fruit weight, and highly positive correlation was found among soluble solids, fructose, glucose and glucose content.