Gengxinshan peat bog has been passing through three periods from eutrophic, mesotrophic to oligotrophic bog, and has correspondingly formed eutrophic wood-herb peat, mesotrophic wood-hreb-moss peat and oligotrophic wood-moss peat. Different types of peat have obviously different physical and chemical properties. Some properties have certain changing law. In the developing process from eutrophic to oligotrophic peat,decomposition degree,pH value, ash content(A^g), calorific value(Q_DT^r), total sulphur content(S_Q^g), phosphorous pentoxide content(P₂O₅), and humic acid content are all evidently decreased; bnt water content(W^f),volatile matter yield(V^r) and organic matter content tend to increasing; contents of SiO₂, Al₂O₃ and TiO₂. in ash are apparently decreased. The reasons resulting in the differences of these properties are related to not only the different climatic environments, nutrient sources and various plant composition in different mire developing stages, but also the organic matter content of peat and the decomposition degree of plant residues and so on.