A　new　single　screw　expansion　machine　was　developed　in　order　to　improve　the　practical　level　of　low　temperature　thermal　power　generation　technology　and　the　utilization　of　waste　heat　and　renewable　energy.　With　compressed　air　as　working　fluid,　the　power,　efficiency,　gas　consumption　rate　and　temperature　difference　of　single　screw　expander　with　rotational　speed　variation　had　been　studied　in　an　established　experimental　apparatus　of　single　screw　expander　[1].　The　results　showed　that,　the　maximum　speed　of　expander　reached　3393r/min,　the　maximum　moment　of　torque　reached　22N.m,　the　maximum　power　of　expander　was　up　to　4.4kW,　and　the　maximum　inlet　flow　rate　was　32.9m3/h.　The　maximum　temperature　difference　between　import　and　export　of　expander　reached　45　degrees　C.　The　lowest　gas　consumption　rate　was　up　to　55.2kg/kW.h,　and　the　maximum　total　efficiency　of　expander　reached　58.8%.