We　present　a　run-based　algorithm　for　identifying　connected　components　in　binary　images.　We　define　affecting　scope　of　a　run　and　use　an　array　whose　size　is　equal　to　width　of　the　image　to　store　runs＇　labels　in　a　row.　The　label＇s　storing　scope　in　the　array　is　the　run＇s　affecting　scope.　By　checking　values　in　the　array　we　can　know　whether　the　current　run　connects　with　any　upper-row　neighbor　runs.　We　also　define　updating　principles　to　maintain　the　array.　The　algorithm　only　needs　to　scan　image　one　pass　and　need　not　maintain　an　equivalent　table,　so　its　speed　is　fast　and　it　is　very　simple.　It　can　identify　4-connectivity　and　8-connectivity　connected　components　in　binary　images.　Experiment　results　show　that　the　algorithm　is　effective.　©　2010　IEEE.