Our　recent　biosystems　analysis　revealed　similarities　between　embryonic　implantation　and　cancer　cell　adhesion,　which　suggests　that　abortifacients　may　be　good　for　safe　and　effective　metastatic　chemoprevention　targeting　circulating　tumor　cells　(CTC).　Here　we　test　the　hypothesis　by　using　the　well-known　abortion　herb　Achyranthes　bidentata　Blume　(A.　bidentata).　Five　compounds　were　separated　from　the　herb　root.　Among　them,　ginsenoside　Ro　was　the　most　potent　in　inhibiting　embryonic　implantation　within　non-cytotoxic　concentrations.　It　specifically　inhibited　the　metastatic　dissemination　capability　of　colon　cancer　cells　HT29,　including　the　migration　and　invasion　ability,　and　their　adhesion　to　human　endothelium　through　inhibiting　integrin　alpha　v　beta　6,　MMP-2,　MMP-9,　and　ERK　phosphorylation　by　HT29.　Pretreatment　of　nude　mice　with　oral　ginsenoside　Ro　followed　by　HT29　intravenous　inoculation　and　40-day　oral　ginsenoside　Ro　significantly　prevented　lung　metastasis　with　downregulation　of　integrin　alpha　v　beta　6　and　no　toxicity.　The　present　study　firstly　introduces　the　new　conception　of　utilizing　safe　and　effective　abortion　botanic　medicines　for　CTC-based　metastatic　chemoprevention.