nvironments in the past researches. But whether or not they can form in the waterbodies only and how about the stability, there are disregardful. We want to determine Pr and Ph forming or not in the modern soil samples from different ecological environments to study the isoprenoids formation and characteristics, so to show the geological significance of Pr/Ph. Methods:The soluble organic nalkanes in the modern surface soils from the midforests, interforests, upper limit forests, lower limit forests, upper limit alpine meadow, and Donggi Cona subalpine desert—meadow in the Gansu, Qinghai and Xizang(Tibet) had been analyzed in this paper. Isoprenoids had been determined based on the m/z85 from the total ion current, and the distribution characteristics and origin of Pr and Ph had been discussed.Results:It is shown that Pr and Ph save in the soils distributing in the different geographical environments not only formed in the waterbodies in the past researched. Pr/Ph ratio is in the range of 0.6~1.4, mean 0.95; Pr/ nC17 ratio is 0.2~1.2, mean 0.64; and Ph/ nC18 is 0.4~1.4, mean 0.85. There is not a clear relative between Pr/Ph and the soils in the different ecological environments, but there is a mid degree relation between Pr/Ph with geographical belts. Conclusions:Pr predominance formed by the microorganisms degrade organic matter under aerobic respiration in the relative warm and wet soils. And Ph predominance formed under the anaerobic fermentation in the relative dry and cold soils. Because different parent materials of Pr and Ph, and different sources from terrestrial and waterbodies, and maybe influenced by the forming of Pr and Ph in the process of thermal evolution and diagenesis, Pr/Ph palaeoenvironmental proxy must be testified to judge which kinds of environmental condition in the sediment basins.