Litchi was rich in nutrients and high in sugar. To investigate the effects of Lactobacillus fermentation on the functional ingredients and glycemic index of litchi, this study employed Lactiplantibacillus plantarum subsp. plantarum, Limosilactobacillus fermentum, and Lactobacillus rhamnosus to ferment litchi pulp. By tracking changes in the viable counts, composition of small-molecule sugars and organic acids, crude polysaccharide and total phenolic contents, and antioxidant activity, the optimal fermentation time was determined; and fermented powder was then prepared to investigate differences in the glycemic index among various powders. The results indicated that, from 0 to 96 h of fermentation, the viable contents of pulp fermented by three Lactobacillus strains increased early and then decreased; the glucose contents decreased from 58.32 mg?g-1 to 20.98, 23.26, and 34.07 mg?g-1, while lactic acid contents increased from 1.86 mg?mL-1 to 17.49, 10.98, and 6.77 mg?mL-1, respectively; the crude polysaccharide contents increased from 0.12 g?100 g-1 to 0.34, 0.31, and 0.28 g?100 g-1, while total phenolic contents increased from 260.16 mg GAE?L-1 to 340.79, 326.51, and 318.57 mg GAE?L-1, respectively; ABTS+ radical scavenging capacity increased from 2.86 mmol TEAC?L-1 to 3.28, 3.11, 3.09 mmol TEAC?L-1, respectively. Unfermented and fermented powders by three types of strains for 72 h were prepared. The values of expected glycemic index (eGI) of unfermented and fermented powders by L. rhamnosus were 64.51 and 56.75, respectively, classified as medium-GI food; while eGI values of fermented powder by L. plantarum and L. fermentum were 54.12 and 53.07, respectively, classified as low-GI food. This study analyzed the effects of different Lactobacillus strains on the functional ingredients of litchi, providing a theoretical basis for the development of low-GI functional litchi products.