Smad　ubiquitination　regulatory　factor　1　(Smurf1)　is　an　HECT　type　E3　ligase　and　regulating　a　lot　of　life　activity,　such　as　nervous　development,　cell　polarization,　bone　remodeling　and　tumor　formation,　etc.　At　present,　it　is　in-deep　that　our　knowledge　about　Smurf1,　but　people　did　not　particularly　distinguish　its　isoform　Smurf1　L　and　Smurf1　S　(the　former　have　26　amino　acid　more　than　the　latter)　in　previous　study,　and　most　of　related　work　tend　to　Smurf1　S.　So　this　article　provided　some　information　about　the　function　of　Smurf1　L　and　Smurf1　S.　By　means　of　RT-PCR,　immunofluorescence　assay　and　Western　blot,　we　studied　the　difference　of　Smurf1　L　and　Smurf1　S　in　some　aspects,　including　tissue　expression,　subcellular　localization　and　substrate　degradation.　The　result　suggested　that:　on　the　one　hand,　not　only　the　tissue　distribution　of　Smurf1　S　is　more　widespread　than　Smurf1　L,　but　also　its　expression　level　is　higher　than　Smurf1　L;　on　the　other　hand,　their　subcellular　localization　have　also　obvious　distinction.　Smurf1　L　exist　at　spindles　in　mitotic　phase,　but　Smurf1　S　perhaps　exist　in　cytoplasm.　In　addition,　the　degradation　ability　to　substrate　of　Smurf1　S　is　stronger　than　Smurf1　L,　and　have　dose-dependent.　In　short,　these　achievement　have　important　significance　for　more　precise　research　to　Smurf1.