A　single-screw　expander　with　155　mm　diameter　screw　has　been　developed.　In　order　to　investigate　the　performance　of　this　prototype　with　different　inlet　vapor　dryness,　an　organic　Rankine　cycle　experimental　system　was　built,　and　experiments　were　conducted　at　different　inlet　vapor　dryness　by　adjusting　the　mass　flow　rate　of　working　fluid　into　evaporator.　The　results　indicated　that　with　the　increase　of　inlet　vapor　dryness,　the　power　output　and　expansion　ratio　were　increased,　however,　the　volume　efficiency　and　overall　efficiency　were　decreased.　The　maximums　of　power　output,　expansion　ratio,　volumetric　efficiency　and　total　efficiency　of　single-screw　expander　were　5.12　kW,　4.55,　80.5%　and　49.5%,　respectively.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.