Located at the transitional zone of loess plateau and northwestern arid area, Lanzhou area developed a set of aeolian red clay and alluvial-lacustrine deposits in the Late Cenozoic. A detailed study of rock magnetism was carried out on these strata and the results show that the magnetic parameters such as magnetic susceptibility are related to the pedogenesis in the details, but in a large trend, they can be used as an indicator of aridification. Like redness, other magnetic parameters such as S-300mT mainly reflect the content of hematite which can be regarded as an indicator of the temperature. The main magnetic minerals in the bottom of the section where alluvial and fluvial-lacustrine had deposited are maghemite, magnetite and hematite.