Objective: To solve the problem of difficult preservation of fresh Mulberry, fresh Mulberry is fermented by Lactobacillus plantarum to produce Mulberry Jiaosu. Methods: Using fresh Mulberry juice as the raw material, Lactobacillus plantarum as strain and total phenol as index, the fermentation process of Mulberry Jiaosu was optimized by single factor test and response surface test. Results: The optimized fermentation conditions were as follows: fermentation time was 40 h, fermentation temperature was 32 ℃, inoculation amount was 25%, and the total phenol content of Mulberry Jiaosu was （43.48±0.67） μg/mL, which was 1.62 times that of non-fermented Mulberry juice. Conclusion: The quality evaluation results showed that the Mulberry Jiaosu had purple red color, uniform color, strong mulberry fruit aroma and fermentation aroma, no peculiar smell, soft sour taste, good flavor, lustre, no impurities and precipitation. The indexes of the Mulberry Jiaosu meet the relevant national standards.