The formationof the Wuhai Broad Valley（WBV）, located at the junction of the Yinchuan Basin and the Hetao Basin, is a visual record of the historical evolution of the end of the upper reaches of the Yellow River.. However, the stratigraphic- -chronological sequence of the Yellow River terraces in this section has not yet been established, and the formation and cutting history of the Yellow River in this area is still unclear. In this paper, based on the field geomorphological, stratigraphic, and sedimentologic investigations, four-level of fluvial terraces are identified on the east side of the WBV and are dated by the Optically Stimulated Luminescence (OSL) dating method. The results show terrace T1 is a depositional terrace with an abandoned age greater than 0.52±0.04 ka. The terraces T2-T4 are base terraces and are characterized by a similar sedimentary sequence consisting of fluvial deposits in the upper part and lacustrine deposits in the lower part. The maximum estimated abandon ages of the terrace T2, T3, and T4 are about 41.98±2.7 ka, 67.48±4.07 ka, and 102.32±6.00 ka, respectively. The average incision rates from T4 to T3, T3 to T2, and T2 to T0 are calculated to be 0.11 mm/a (~102-67 ka), 0.24 mm/a (~67-42 ka), and 0.26 mm/a (42 ka-modern), showing a gradual increase incision rate since ~102 ka. The age of the lacustrine deposits in the terraces T2-T3 coincides with the development time of the Late Pleistocene “Jilantai-Hetao Megalake”, indicating that the range of megalake had already reached the study area at that time. The formation of the fluvial terraces in the study area was developed in the process of narrowing and disappearing of the “Jilantai-Hetao Megalake”, which represents the transition between lake-river landform at the upper reaches of the Yellow River in the Late Pleistocene. Through detailed comparisons with the low-level sequences of various fluvial terraces around the Ordos Block, combined with regional tectonic and climatic information, it is concluded that the formation of the Late Pleistocene fluvial terraces in the WBV and the transition between lake-river landform were mainly controlled by tectonic activities.