In　space　heating,　air　source　heat　pumps　(ASHPs)　always　encounter　mal-defrosting　incidents,　resulting　in　significant　energy　waste.　To　improve　the　defrosting　accuracy　of　ASHP,　this　paper　proposes　a　novel　Time-CurrentTemperature　difference　(T-I-T)　defrosting　control　method　based　on　the　characteristic　parameter　of　outdoor　fan　operation　(current).　Through　theoretical　analysis　and　experimental　tests,　the　influence　of　frosting　on　the　characteristic　parameters　of　outdoor　fan　operation　was　revealed.　Then,　based　on　the　optimal　defrosting　control　point　theory,　a　method　for　selecting　the　defrosting　current　threshold　close　to　the　actual　ASHP　was　proposed.　Ultimately,　a　novel　Time-Current-Temperature　Difference　(T-I-T)　defrosting　control　method　was　developed,　using　the　current　increment　to　control　the　defrosting　operation.　The　results　showed　that,　the　defrosting　current　thresholds　decreased　as　the　severity　of　frosting　decreases,　from　1.52　to　0.78　A.　The　T-I-T　defrosting　control　method　enables　the　ASHP　unit　to　operate　stably　and　efficiently　in　space　heating.　The　defrosting　frequency　decreased　from　0.93　to　0.56　times　per　hour,　a　reduction　of　39.80　%;　the　average　duration　of　the　frosting/　defrosting　cycle　increases　from　64.30　to　106.90　min　(an　increase　of　66.25　%),　and　the　average　COP　of　the　ASHP　unit　increases　by　10.60　%　compared　to　the　T-T　defrosting　control　method.