Abstract: After preacidification,Streptococcus mutans international standard strain and LuxS mutant strain were cultivated in BHI liquid culture medium with a pH gradient acidic environment in order to study the growth and glucose uptake of Streptococcus mutans after LuxS mutation in vitro. The two strains were preacidificated in BHI liquid culture medium with pH5.5, the initial pH value was set at 6.0~7.0, and the glucose uptake of the Streptococcus mutans LuxS mutant and international standard strain from the BHI medium was measured by the glucose oxidase method under the pre-acidification and non-acidification conditions. The glucose uptake of LuxS mutant strain was significantly less than that of international standard strain at pH6.0~7.0(P<0.01). The glucose uptake of the LuxS mutant strain from preacidified culture was more than that which did not to be deal with(P<0.05). The glucose uptake ability of the Streptococcus mutans LuxS mutant decreased, LuxS mutant had a weaker cariogenic potential than international standard strain.