Composition　of　web　services　has　received　much　interest　to　support　business-to-business　or　enterprise　application　integration.　Web　service　composition　lets　developers　combine　single　services　as　a　composite　one　to　achieve　complex　goal.　It　is　a　highly　complex　task　and　already　beyond　the　human　capability　to　deal　with　the　whole　process　manually,　so　AI-based　approach　for　automated　web　service　composition　has　drawn　much　research　attention.　AI-based　service　composition　uses　some　algorithm　in　Artificial　Intelligence,　such　as　AI　planning　and　graph　searching.　Based　on　analysis　of　the　limitation　of　those　two　approaches,　an　AND/OR　treebased　approach　for　web　service　composition　is　proposed　in　this　paper　which　is　based　on　Artificial　Intelligence.　The　Input/Output　Dependency　AND/OR　Tree　is　represented　first,　and　then　AND/OR　tree　search　algorithm　including　basic　search　algorithm　and　special　algorithm　is　discussed.　With　that,　an　implementation　is　provided　to　described　whole　process　when　apply　AND/OR　Tree　search　algorithm　in　web　service　composition　field.　©　2008　IEEE.