During　the　space　heating　in　winter,　the　air　source　heat　pump　(ASHP)　often　encounters　frosting　problem.　In　former　studies,　it　was　found　that　the　frosting　performance　of　ASHP　and　indoor　thermal　environment　vary　significantly　when　the　supply　water　temperature　changes.　However,　the　influence　mechanism　of　supply　water　temperature　is　still　unknown.　To　solve　this　problem,　the　frosting　performance　variations　of　ASHP　and　its　effect　on　indoor　thermal　environment　variations　at　the　supply　water　temperature　of　41–50　℃　were　investigated　in　the　psychrometric　chamber　and　artificial　environmental　chamber,　respectively.　Results　showed　that　increasing　supply　water　temperature　can　effectively　suppress　the　frosting　speed　and　reduce　the　impact　of　frosting-defrosting　on　indoor　thermal　environment.　When　the　supply　water　temperature　raises　from　30　℃　to　50　℃,　the　frosting　duration　prolongs　from　50　min　to　101　min.　Meanwhile,　the　indoor　temperature　drop　caused　by　frosting-defrosting　decreased　by　about　45　%　when　supply　water　temperature　rises　from　41　℃　to　50　℃.　Besides,　with　the　increase　of　supply　water　temperature,　the　impact　of　frosting　on　the　heating　performance　of　the　ASHP　decreases.　When　it　rises　from　30　℃　to　50　℃,　the　attenuation　degree　of　the　average　coefficient　of　performance　during　frosting-defrosting　cycle　drops　from　9.85　%　to　7.25　%,　compared　to　those　at　non-frosting　condition.　However,　although　the　frosting　performance　of　ASHP　and　its　effect　on　indoor　thermal　environment　both　get　better　with　the　increase　of　supply　water　temperature,　the　overall　heating　performance　of　the　ASHP　still　declines.　©　2024　Elsevier　Ltd