In　order　to　resolve　the　issue　of　containing　query　with　a　node　set　formed　by　multi-keywords,　this　paper　proposes　an　index　structure,　named　PS-Tree,　and　applies　it　to　a　semantic　search　engine.　The　PS-Tree　refers　to　a　set　attribute　index　of　object-orient　database.　It　can　map　user＇s　query　to　a　semantic　path　which　contains　semantic　relations　as　the　aim　of　user＇s　query　in　form　of　multi-keywords　by　＇range　query＇.　It　can　improve　the　performance　of　index　structure.　The　experiment　result　shows　that　the　PS-Tree　gives　a　good　performance　especially　when　there　is　a　long　semantic　distance　between　the　query　keywords.