To confirm the effects of binlang(Areca catechu L.) and tansen(Salvia miltriorrhiza bung) on the mutagenicity induced by hydrogen peroxide, SOS Chromotest with Escherichia coli PQ37 and Ames test with Salmonella typhimurium TA104 were perlormed. Methanol-soluble parts of their water extracts showed high inhibitory effect against the mutagenicity of hydrogen peroxide in two bacterial mutation assays. Step-wise fractionation of methanol-soluble part from tansen was done using ethyl acetate, butanol and water. Among these fraction was further partitioned by Sephadex LH-20 column chromtography, and 6 subfractions were obtained. The fraction III showed the strongest inhibitory effects against the mutagenic activities induced by hydrogen peroxide. The inhibition rates of fraction III at concentration of 500$mu extrm{g}$/assay were 28%, 30% and 15% against 4-NQO, MNNG and B(a)P, respectively. But the mutagenic potency of AFB1 was increased.