A　single-screw　expander　has　been　designed　and　manufactured　independently.　Based　on　this　prototype,　testing　system　has　been　built　and　performance　experiment　has　been　made.　In　this　article,　compressed　air　was　used　as　working　fluid　and　performance　test　for　the　prototype　was　finished　at　conditions　including　different　rotational　speed　and　different　inlet　pressure.　From　the　experimental　data,　it　is　shown　that　when　inlet　pressure　less　than　0.8MPa　the　output　power　increases　with　the　increase　of　rotational　speed　because　of　not　enough　expansion;　when　inlet　pressure　more　than　0.8MPa,　the　every　biggest　output　power　is　appeared　in　the　condition　of　rotational　speed　2600　rpm.　The　test　results　also　show　that　the　total　efficiency　is　influenced　by　rotational　speed　obviously,　and　the　highest　total　efficiency　of　this　machine　is　69.64%　in　the　condition　of　3000　rpm　and　15　bar.