A series of allochthonous and autochthonous molecular fossils were identified from the Holocene paleosol (S0), Malan Loess (L1) and the top Lishi Loess (S1) in Jiuzhoutai loess profile in Lanzhou through the GC/MS analysis. The allochthonous molecules were transported into the Plateau by the loess grains whilst the autochthonous molecules were related to the input of the local paleo-vegetation and could be used to reconstruct the paleo-vegetation. The distribution of the autochthonous n-alkanes was discriminated from the overlapping allochthonous homologues characterized by the CPI value of unity. The dominance of autochthonous C31 n-alkane implicates the occurrence of a grassy vegetation over the Loess Plateau since the last interglacier. The warmest period of the Holocene, though dominated by grass, was additionally characterized by the relatively increased abundance of C27 n-alkane indicative of woody plants. The desert plants might occur during the last glacier. The molecular fossil record is not con A series of allochthonous and autochthonous molecular fossils were identified from the Holocene paleosol (S0), Malan Loess (L1) and the top Lishi Loess (S1) in Jiuzhoutai loess profile in Lanzhou through the GC / MS analysis. The allochthonous molecules were transported into the Plateau by the loess grains while the autochthonous molecules were related to the input of the local paleo-vegetation and could be used to reconstruct the paleo-vegetation. The distribution of the autochthonous n-alkanes was discriminated from the overlapping allochthonous homologues characterized by the CPI value of unity. The dominance of autochthonous C31 n-alkane implicates the occurrence of a grassy vegetation over the Loess Plateau since the last interglacier. The warmest period of the Holocene, though dominated by grass, was less characterized by the relatively increased abundance of C27 n-alkane indicative of woody plants. The desert plants might occur during the last glacier. The molecular fossi l record is not con