The　characteristics　of　frost　formation　and　heat　transfer　of　fins　with　cryogenic　fin　base-temperature　under　natural　convection　were　studied.　The　air　relative　humidity　has　significant　effects　on　frost　formation.　The　main　parameters　of　frost　layers　change　in　the　similar　range　with　the　same　air　relative　humidity　in　experiments.　Effects　of　fin　base-temperature　are　weak　on　frost　layer　growth,　but　there　is　still　a　weak　trend　that　the　frost　layer　thickness　increases　with　the　decrease　of　fin　base-temperature.　With　the　increase　of　air　relative　humidity,　the　thickness　of　the　frost　layer　increases,　but　the　heat　flux　and　heat　transfer　ratio　of　fins　increase.　The　physical　properties　of　frost　layers　play　a　decisive　role　in　the　heat　transfer　through　frost　layers.　©　2020,　Science　Press.　All　right　reserved.