In　practical　projects,　it　is　found　that　at　the　same　outdoor　temperature　and　relative　humidity,　the　frosting　per-formance　of　variable-frequency　air　source　heat　pumps　(VFASHPs)　in　different　climatic　regions　varies　obviously,　e.g.　frost　will　be　accumulated　on　its　outdoor　coil　at　the　condition　of　3　degrees　C,　90　%　in　Beijing,　but　not　in　Harbin.　To　reveal　the　frosting　performance　variations　of　VFASHPs　in　different　climatic　regions,　a　mathematical　model　of　VFASHPs　was　established,　and　its　frosting　maps　in　cold　region　and　hot-summer　and　cold-winter　region　were　developed.　Combining　its　frosting　map　in　severe　cold　region　obtained　from　experiments,　its　frosting　performance　variations　in　three　climatic　regions　were　investigated.　Results　indicate　that　when　a　VFASHP　is　used　in　different　climatic　regions,　its　frosting　region　varies　obviously.　In　different　climatic　regions,　when　the　outdoor　design　temperature　for　heating　is　lower,　its　critical　relative　humidity　for　frosting　is　higher;　while　the　upper　and　lower　limit　temperatures　of　frosting　region　are　both　lower.　Taken　0　degrees　C　as　an　example,　the　critical　relative　humidity　for　frosting　in　Harbin,　Beijing,　and　Shanghai　are　79.3　%,　66.2　%,　and　55.0　%,　respectively.　This　work　can　provide　guidance　for　defrosting　control　strategy　design　of　VFASHP　in　different　climatic　regions.