Five main groups of soils close in their thermal properties and depth of permafrost layer seasonal thawing are distinguished on the basis of thermal regime studying of Southern Yamal forest-tundra (West Siberian plain western margin) cryogenic soils. The change in seasonally thawing layer thickness was studied as well as data for the thermal profile of these soils were obtained for four of them on the permanent monitoring sites in the period from 2012 till 2017 A significant spatial variation of the active layer thickness is show. It depends on meso- and microrelief conditions, properties of parent rocks and soils, vegetation state and type, significantly exceeding the interannual fluctuations associated with climatic rhythms and trends. The amount of precipitation in the warm season is apparently the most affected climatic parameter which influence on the depth of seasonally thawing layer.