Interactions between Streptococcus salivarius and Streptococcus mutans play important roles in the development of dental biolms in oral cavity. S. salivarius BD3900, isolated from the oral cavity of a healthy voluteer, displayed the potential to be an oral probiotics in vitro. Strong hydrophobicity (95.8%) and high surface charges(≥88.6%) endure the strain to be easily adhered in oral cavity. The strain BD3900 was tolerant to 100 μg/mL lysozyme(2.0×104 U/mg), indicating the high ability for the strain to survive in oral cavity. Besides, the strain was determined to be with high auto-aggregating ability(15%～20%) as well as co-aggregating abiltity with Streptococcus mutans.in the presence of sucrose at a concentration dependant manner, with a highest co-aggregation rate of 64.3% at a sucrose level of 5 g/100 mL, while no obvious effect of sucrose was observed on the auto-aggregation of the strain BD3526. Furthermore, when co-cultured with the strain BD3900, the formation of S. mutans biofilm could be reduced by 67.1%. Therefore, the strain S. salivarius BD3900 is a candidate of oral probiotics with potential in prevention of dental caries.