Frost　deposition　phenomena　on　cryogenic　cold　surfaces　are　receiving　more　and　more　attention　from　both　researchers　and　various　industries.　However,　frost　formation　on　fins　of　cryogenic　temperature　has　been　not　touched.　Therefore,　an　experimental　system　of　frost　deposition　on　straight　cylindrical　fins　with　fin　base　temperature　as　low　as　-190　degrees　C　under　natural　convection　conditions　was　established　and　a　series　of　frost　formation　experiments　under　various　conditions　were　carried　out　to　analyze　the　characteristics　and　influence　factors　of　frost　formation.　The　results　show　that　due　to　the　change　of　frost　formation　mechanism,　the　frost　formation　on　the　fin　is　greatly　different　under　different　temperature　ranges.　The　distribution　of　the　frost　layer　thickness　on　the　fins　at　cryogenic　temperature　is　more　uneven　along　both　the　fin　axial　and　circumferential　directions,　and　this　characteristic　is　more　significant　in　the　early　frost　stage.　The　frost　formation　mechanism　changes　not　only　with　the　base　temperature,　but　also　along　the　fin　length　when　the　base　temperature　is　low　enough.　For　low　fin　base　temperatures,　say　-190　degrees　C,　liquid　air　appears　at　the　fin　base,　which　will　lead　to　no　frost　in　the　near-fin-base　region　for　a　long　time,　and　lowering　the　fin　base　temperature　will　decrease　frost　layer　thickness.　The　size　of　the　near-fin-base　region　increases　as　the　fin　base　temperature　decreases.　In　addition,　increasing　air　relative　humidity　or　air　temperature　without　changing　other　conditions　will　accelerate　frost　formation.　The　results　also　show　that　fin　materials　strongly　affect　the　distribution　of　frost　layer　on　fins.