Objective:　To　research　the　mechanism　of　the　inhibition　effects　of　BWE　on　cell　attachment　of　influenza　virus　by　capillary　electrophoresis.　Method:　The　morphologic　difference　of　red　cells　after　treating　with　BWE　infected　by　influenza　virus　was　detected　with　microscope,　capillary　electrophoresis　and　HA.　Result:　The　pretreatment　of　the　normal　cells　with　BWE　inhibited　the　attachment　of　influenza　to　the　cells,　while　no　meaningful　inhibition　was　observed　when　influenza　virus　was　pretreated　before　being　inoculated　to　cells.　Conclusion:　The　results　indicate　that　the　inhibition　effects　of　BWE　on　cell　attachment　of　influenza　virus　may　be　an　important　mechanism　of　anti-influenza　activity　of　Radix　Isatidis　Extracts.