This paper describes the preliminary research on lipids from So to L₉ loess—paleosol sequence of Duanjiapo section near Xi’an,which include total organic matter content, lipid characteristics and magnetite of organic matter. The loess has a low content of organic matter (<1.5%),its content and nature are related to environment states.The natural vegetation thrives when climate is warm/humid and the content of organic matter is high.When it is dry/clod,the natural vegetation is sparse and scattered and the content of organic matter is low.Therefore,the content is a reflection of the biomass. The content curve of organic matter is similar to fine silt fraction (<1μm)curve. Muhivalent cations link organic colloids of each other and to clays to form aggregates.This organo-sih fraction also appears to be highly resistant to degradation of organic matter.It changes the soil geochemical environment to one which is conductive to the formation of soil magnetite.The majority of organic matter was formed by natural vegetation decomposition during pedogenesis.This is an integrated environment,with small areas where reduction occurs.But the whole system is generally in one state of oxidization.