Micro-structural characteristics of loess in the Xianyang downtown area were revealed using scanning electron microscope.Results show that loess microstructures are horizontally different with different landscape units,and vertically vary with different loess layers.The micro-structural difference between loess layers and paleosols in a given profile is most obvious.Loess layers mainly have supporting-macrospore and mosaic-microspore semi-cementation structures,whereas paleosols mainly have flocculent and coagulum cementation structures.Within a landscape unit,loess in the third and second terraces of the Weihe River is mainly characterized by supporting-macrospore and mosaic-microspore semi-cementation structures,and loess in the first terrace,by mosaic-microspore and flocculent cementation structures.Structure characteristics are mainly controlled by the environments of sedimentation,soil formation and loess burying.