The　ratio　and　the　diameter　of　artery/vein　of　the　retinal　can　reflect　the　risk　of　stroke　of　hypertension,　thus,　quantitative　analysis　of　the　diameter　of　the　vessel　can　contribute　to　risk　assessment　and　prevention　of　the　disease.　A　artery/vein　automatic　classification　method　in　Retinal　Images　and　Vessel　Diameter　Measurement　are　introduced　in　this　paper.　Firstly,　the　vessel　centerline　is　obtained　after　segmenting　the　retinal　vessel.　Secondly,　different　channel　components　in　different　color　spaces　are　selected,　the　eigenvectors　of　centerline　pixels,　vessel　pixels.　vessel　widths　and　central　light　reflection　are　defined.　K-means　clustering　algorithm　is　adopted　to　classify　the　artery/vein　in　the　measurement　region　of　interest.　Finally,　the　distribution　curve　of　the　vessel　cross　section　is　fitted　using　the　Gaussian　curve　and　the　width　of　the　artery/vein　can　be　obtained　according　to　Half　Height　Full　Width.　Experiments　with　Review　public　database　and　Drive　public　database　prove　the　effectiveness　of　the　proposed　method.　©　2017,　Science　Press.　All　right　reserved.