We investigated the inhibition effects of teeth decalcification and glucosyltransferase(GTase) activity on the Juniperus rigida S. et Z. Teeth decalcifications by Streptococcus mutans were respectively inhibited to 70.13, 74.93% on methanol and n hexane fractions. In the inhibition test of GTase activities by solvent fractions of J. rigida, they were respectively inhibited to 86.6, 89.5% to a similar degree. And in the result to identify GTase produced by S. mutans with SDS PAGE, the band near 65KD estimated as GTase did not show in the lanes of methanol, n hexane and chloroform fractions.