This　paper　focuses　on　semi-actuated　signal　algorithm　with　the　affect　of　the　crossing　pedestrian-bicycle　groups　on　left-turn　vehicles　at　two-phase　intersections.　The　paper　analyzed　the　conflict　characteristic　of　left-turn　vehicles　with　pedestrian-bicycle　groups,　and　made　good　efforts　to　study　gap-acceptance　with　field　data　collected　in　Huairou　District　of　Beijing.　According　to　the　balance　principle　of　the　left-turn　vehicles　arriving　and　departing,　the　new　minimum　green　interval　algorithm　model　is　built,　and　it　is　validated　with　the　field　test.　The　minimum　green　time　value　result　with　the　new　algorithm　is　bigger　than　that　determined　with　HCM2000,　which　means　it　can　make　up　the　lost　time　of　left-turn　vehicles　for　the　affects　of　crossing　pedestrian-bicycle　groups.　As　demonstrated　in　the　field　study　at　the　intersection　of　Yingbin　Road　and　Fule　Street　in　Huairou　District,　the　timing　plan　calculated　with　the　new　algorithm　adapted　to　the　intersection　situations　perfectly.　The　total　control　delay　of　the　whole　intersection　decreased　37.8　percentile,　and　the　LOS　(Level　of　Service)　of　whole　intersection　improved　from　C　to　B.　©　2010　ASCE.