In　order　to　recover　the　pressure　energy　of　high　pressure　natural　gas　in　letdown　station,　a　high　pressure　single　screw　expander　(HPSSE)　with　117　mm　diameter　replace　the　pressure　reducing　valve　is　developed　in　our　lab　recently.　In　this　paper,　an　experimental　system　for　high　pressure　energy　recovery　has　been　built　using　high　compressed　air　as　working　fluid　and　the　performance　of　this　HPSSE　has　been　tested　under　varied　inlet　pressure　and　rotational　speed.　Results　show　that,　the　best　performance　of　HPSSE　is　obtained　with　the　maximum　power　output,　volumetric　efficiency,　shaft　efficiency　and　the　lowest　air-consumption　ratio　is　33.2　kW,　86.45%,　51.9%　and　58.8　kg/(kW•h),　respectively;　The　volumetric　efficiency　increases　with　the　increase　of　rotational　speed,　but　the　inlet　pressure　has　less　influence　on　it;　The　shaft　efficiency　increases　with　the　increase　of　rotational　speed,　and　it　first　increases　and　then　gradually　stabilize　with　the　increase　of　inlet　pressure;　The　air-consumption　rate　decreased　with　the　increase　of　rotational　speed,　and　it　first　decreases　and　then　increases　with　the　increase　of　inlet　pressure.　©　2020,　Science　Press.　All　right　reserved.