Abstract: Lychee juice was fermented with Lacticaseibacillus casei, Lactococcus lactis subsp. lactis, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactiplantibacillus plantarum, and Leuconostoc mesenteroides subsp. cremoris to study the effects of fermentation on the physicochemical properties, major active ingredient content, antioxidant capacity, and effects on defecation and small intestinal motility in mice. The results showed that fermentation with various probiotics decreased the pH of lychee juice while increasing total acid and soluble solids content. After fermentation, the total phenol and total flavonoid content, as well as the antioxidant capacity of lychee juice, decreased to varying degrees, while the polysaccharide content increased by 9.38 to 13.31 times. Specifically, lychee juice fermented with Lacticaseibacillus casei and Lactobacillus delbrueckii subsp. bulgaricus retained more active components and antioxidant activity. The experimental results in mice showed that the group of lychee juice fermented with Lacticaseibacillus casei shortened the time of first defecation by 47.39% compared to the model group. The quantity, weight and water content of red stool particles within 6 hours were significantly higher than those in the model group (P<0.05), and the rate of eosin advancement was not statistically different from the control group (P>0.05). Therefore, lychee juice fermented with Lacticaseibacillus casei has a greater laxative effect, providing a theoretical basis for the further development of functional fermented lychee juice products.