Research　and　development　of　renewable　energy　is　one　solution　to　energy　crisis　and　its　related　environmental　problem.　Among　all　kinds　of　renewable　energy,　geothermal　energy　has　good　development　feasibility　due　to　its　low　investment　and　operation　costs,　independence　to　weather　and　climate　change,　and　stable　power　generation.　In　China,　high　temperature　geothermal　resource　is　rare;　however,　low-medium　temperature　geothermal　resource　is　widely　distributed.　Therefore,　small　and　medium　sized　geothermal　power　system　based　on　low-medium　temperature　organic　Rankine　cycle(ORC)　is　a　good　choice　for　geothermal　exploitation.　Expander　is　the　key　device　in　such　system.　Single　screw　expander　has　proper　size　and　good　output　performance.　Therefore,　in　order　to　test　the　application　of　single　screw　expander　in　geothermal　exploitation,　compressed　air　was　used　as　working　fluid　to　conduct　experimental　study　at　different　temperature.　The　results　show　that　at　the　same　rotational　speed,　the　single　screw　expander　at　a　higher　air　temperature　has　a　bigger　output　power,　a　smaller　gas　consumption　rate,　a　bigger　expansion　ratio,　a　bigger　temperature　drop,　a　higher　thermal　efficiency,　and　a　smaller　irreversible　loss.　Moreover,　if　a　lubricant　circle　is　added　in　the　experimental　system,　the　single　screw　expander　with　lubricant　at　a　lower　air　temperature　will　have　the　same　performance　as　the　expander　without　lubricant　at　a　higher　air　temperature.　Therefore,　the　performance　of　single　screw　expander　can　be　improved　by　adding　a　lubricant　circle　and　raising　compressed　air　temperature.　(C)　2014　The　Authors.　Published　by　Elsevier　Ltd.