Air-cooled　frost-free　household　refrigerators　have　become　popular　in　the　market　because　of　their　large　storage　volume　and　frost-free　compartments.　However,　the　large　amount　of　power　consumed　by　the　defrosting　process　of　the　evaporator　restricts　the　widespread　application　of　such　refrigerators.　In　this　study,　a　new　type　of　defrosting　system　using　outdoor　air　(DSUOA)　is　developed.　The　operation　modes　(refrigeration　and　defrosting　cycles)　of　the　overall　system　are　proposed.　An　experimental　prototype　is　built,　and　an　experimental　study　is　conducted　for　different　temperature　ranges　(12-22　degrees　C,　22-45　degrees　C,　and　0-12　degrees　C).　Results　show　that　the　power　consumption　of　DSUOA　is　77.6-98.2%　less　than　that　of　the　electric　heater　defrosting　system　under　a　similar　defrosting　time.