Intestinal flora is a key factor influencing human health, and dietary fibers play an important role in regulating the balance of intestinal flora. In this study, based on the in vitro digestion experiment of Qingyi brand resistant dextrin, the effects of resistant dextrin on the in vitro growth of Lactobacillus bulgaricus and Lactobacillus casei were investigated, and the differences between resistant dextrin and other dietary fibers in the in vitro proliferation of the two kinds of probiotics were compared and studied. The results showed that the maximum degrees of hydrolysis of Qingyi brand resistant dextrin in simulated gastric and intestinal fluids were 1.32% and 3.67%, respectively, indicating that the product possessed good gastrointestinal digestion-resistant properties. Although the resistant dextrin could not be used as a sole nutrient carbon source to promote the proliferation of two probiotics, but under the condition of ensuring nutrient source, the addition of a certain amount of resistant dextrin to basal nutrient medium could promote the in vitro growth of the strains, and the better amounts for addition to the basal media were 0.6% and 0.4% (m/m) for Lactobacillus bulgaricus and Lactobacillus casei, respectively. Moreover, compared with the addition of other dietary fibers, such as polydextrose, inulin and fructooligofructose, resistant dextrin enabled a greater extent of proliferation of two probiotics, with the OD600 values at the stable phase reaching 2.0, indicating that the utilization rate of resistant dextrin was greater. The results of this study provide a theoretical support for the effective regulation of intestinal flora by water-soluble resistant dextrin.