In this study, we investigated to elevate the modulatory effect of flavonoid(fustin, sulfuretin, 10 mg/kg) which was isolated from Rhus verniciflua Stokes(RVS) in male Sprague-Dawley rats for 2 weeks on the toxicity of paraquat. In the flavonoids pretreated groups, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, blood urea nitrogen, creatinine, malondialdehyde and alkaline phosphatase activity in serum and malondialdehyde, alkaline phosphatase activity and collagen in lung tissue which was induced paraquat toxicity were slightly decrease compared to the normal group. In the lung tissue of flavonoids pretreated groups, malodialdehyde value, G-6-phosphatase activity and collagen synthesis were recovered to tile normal values and alkaline phosphatase activity was increased. From these results, we concluded that flavonoids which were isolated from RVS is an effective agent to inhibit the pulmonary and internal toxicities and hence we concluded that acitive components of fustin and sulfuretin which were isolated from RVS might be removed free radicals induced by paraquat.