According to the analyses and studies of the grain-size, sporopollen, vertebrate fossils and stratum sedimentary facies in the upper pleistocene strata of the Salawusu River area, this paper discusses the palaeogeographic environment and its evolution during the late pleistocene.1.The palaeogeographic environment of the fluviolacustrine facies strata of the Salawusu Formation formed in the early stage of the upper pleistocene is warm-hummid forest steppe.2.In the late stage of the late pleistocene, the Chengchuan Formation which mainly consists of aeolian sandy deposits chiefly forms under dry-cold desert, desert steppe and in the meantime, it underwent a series of alternating evolution processes of temperate-cool's shrub steppe,sparse woods steppe and forest steppe with this environment.3.The Malan loess in the area has the same geological age as that of dry cold desert steppe.4.The Salawusu Formation is assigned to the Riss/Wurm intcrglacial age, dating back to 1.1×10⁵-7×10⁴ yrs B.P.,thereas the Chengchuan Formation andthe Malan loess are in the Wurm glacial age with an assumed date of 7×10⁴-1×10⁴ yrs B.P..