AIM:To study the antivirus constituents of radix of Isatis indigotica METHOD:Various chromatographic techniques were used to isolate and purify the chemical constituents.The structures were elucidated by spectral analysis.The antivirus activity was detected by the chick embryo method.RESULT: Three compounds were identified as 2,4(1H,3H)-quinazolinedione(Ⅰ),epigoitrin(Ⅱ) and indirubin(Ⅲ);compound Ⅱ possessed the action of antivirus activity.CONCLUSION:Epigoitrin(Ⅱ)is the one of main antivirus constituents of Radix of Isatis indigotica.