Addressing　the　growing　need　of　oil-free　compressed　air　has　drawn　the　development　of　the　water　lubricated　single-screw　air　compressor　(WLSSAC).　For　WLSSAC,　clearance　height　is　an　important　design　parameters　relevant　to　compressor　performance.　In　this　study,　a　thermodynamic　model　of　the　working　process　of　a　WLSSAC　is　established　in　consideration　of　the　viscous　friction　power　consumption　and　mass　transfer　between　water　and　wet　air.　The　theoretical　model　is　simulated　by　Matlab　software,　and　the　accuracy　of　the　theoretical　model　is　verified　by　experimental　results.　The　influence　of　each　leakage　path　on　the　rate　of　leakage　flow,　viscous　friction　power　consumption,　and　efficiency　are　analyzed　using　the　proposed　model.　The　effects　of　clearance　height　on　adiabatic　efficiency,　volumetric　efficiency,　and　specific　power　are　calculated　and　discussed.　Results　show　that　the　viscous　friction　power　consumption　caused　by　wall　velocity　decreases　gradually　with　the　increase　in　clearance　height,　while　the　viscous　friction　power　consumption　caused　by　pressure　difference　increases　gradually　in　each　leakage　path.　With　the　increase　in　clearance　height,　the　rate　of　leakage　flow　increases　gradually,　the　adiabatic　and　volumetric　efficiencies　decrease　gradually,　and　the　specific　power　increases　gradually.　The　clearance　height　is　recommended　to　be　0.03e0.06　mm　for　the　design　of　WLSSAC.(c)　2022　Elsevier　Ltd.　All　rights　reserved.