To investigate the anti-caries effect of Ramulus mori oligosaccharides microcapsules, the in vitro cariescausing dental plaque biofilm model was constructed by inoculating natural saliva and Streptococcus mutans on the surface of hydroxyapatite tablets, before culturing for 21 days. The caries-causing dental plaque biofilm model was treated daily via soaking with low, medium and high doses (24.00, 48.00 and 96.00 mg/mL) of Ramulus mori oligosaccharides microcapsules solution to evaluate its anti-caries effect. The results showed that Ramulus mori oligosaccharides microcapsules could effectively destroy the structure of the dental plaque biofilm, and the biofilm thickness (65.95 μm) was significantly reduced in the high dose group compared with the control group (103.08 μm) (P<0.05). The number of bacteria adhering to the surface of hydroxyapatite tablets was reduced upon the treatment with Ramulus mori oligosaccharides microcapsules, resulting in the death of bacteria inside the plaque biofilm and the reduction of biofilm’s activity. The microhardness values (244.25, 265.25) and the calcium-phosphorus ratios of the hydroxyapatite tablets (1.20, 1.49) treated with medium and high doses (48.00, 96.00 mg/mL) of Ramulus mori oligosaccharides microcapsules solution significantly increased compared with the control group (P<0.05). Ramulus mori oligosaccharides microcapsules could effectively reduce enamel demineralization. The high-dose Ramulus mori oligosaccharides microcapsules had the best anti-caries effect. This study aimed to provide a theoretical basis for the development of anti-caries functional foods and daily chemical products from Ramulus mori.