Abstract: The Pleistocene strata with stable regional extension in the southeast Inner Mongolia are divided by pollen assemblages and optically stimulated luminescence (OSL) dating. The eolian sediment of the middle Pleistocene with good columnar joint and OSL age from (40.4±1.9)ka to (110.0±7.5)ka, corresponding to the Wuerji Formation, is composed of yellow sandy loam, calcareous nodule and Artemisia-Ephedra-Pinus pollen assemblages. The lower Pleistocene with OSL age from (200.9±9.6)ka to (220.4±13.2)ka, corresponding to the Chifeng Loess, is composed of reddish brown sandy loam, sandy clay, calcareous nodule, gravel lens and Artemisia-Polygonum-Betula pollen assemblages. These provide basic data for Quaternary stratigraphic correlation and division in the southeast Inner Mongolia.