Horizontal　spiral　coil　ground　heat　exchanger　(HSGHE)　has　been　used　in　ground　source　heat　pump　due　to　its　efficiency　and　low　cost.　The　influence　laws　of　different　factors　on　thermal　performance　of　HSGHE　are　vital　for　its　optimal　design　and　operation.　In　this　paper,　a　small　scale　test　device　of　HSGHE　was　constructed　to　investigate　thermal　performance　of　HSGHE　with　different　inlet　temperatures,　spiral　pitches,　surface　wind　speeds,　and　coil　styles.　The　results　indicate　that　the　soil　temperature　interference　distance　is　about　0.4　m　for　various　inlet　temperatures　under　the　test　conditions.　At　the　same　time,　reducing　spiral　pitch　can　increase　total　HER,　but　it　also　decreases　the　HER　per　unit　length　of　pipe.　As　for　surface　wind　speed,　the　heat　transfer　of　HSGHE　can　be　enhanced　by　increasing　surface　wind　speed,　and　the　shallower　the　burial　depth,　the　better　the　heat　transfer　enhancement　effect.　As　far　as　heat　transfer　performance　is　concerned,　the　spiral　coil　is　superior　to　slinky　coil,　but　the　slinky　coil　is　higher　than　spiral　coil　in　terms　of　soil　thermal　interference.　From　angle　of　improving　heat　exchange　efficiency,　it　is　advisable　to　increase　wind　speed　and　inlet　fluid　temperature,　reduce　the　pitch　and　use　spiral　coil.　A　3-D　numerical　model　has　been　developed　by　COMSOL　soft　to　further　explore　the　influences　of　operation　modes,　soil　types　and　coil　diameters　on　thermal　performance　of　HSGHE.　The　simulation　results　indicate　that　the　soil　temperature　can　be　restored　to　a　certain　extent　by　using　intermittent　operation　mode.　The　longer　the　interval　time,　the　better　the　soil　temperature　resume　and　the　more　obvious　the　improvement　of　thermal　performance.　For　the　effects　of　soil　type,　the　sandstone　has　the　best　heat　transfer　effect,　followed　by　sand,　and　the　clay　is　the　worst.　Nevertheless,　in　term　of　reducing　the　soil　thermal　interference,　clay　is　the　most　advantageous.　Additionally,　increasing　the　coil　diameter　can　improve　total　HER　of　HSGHE　slightly,　but　it　will　also　cause　the　reduction　of　the　HER　per　unit　length.　Therefore,　the　coil　diameter　should　be　set　reasonably　according　to　the　specific　conditions　in　the　engineering　design.　(C)　2019　Elsevier　Ltd.　All　rights　reserved.