Bioassay-directed fractionation of the dired roots of Sophorae Radix led to the isolation of Sophoraflavanone G. Their structures were elucidated using 1H-NMR, 13C-NMR, UV, IR and mass spectral ananlyses. These compounds exhibited a moderate antimicrobial activities against Streptococcus gordonii, Actinobacillus actinomycetemoomitans and Porphylomonas gingivalis.