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Comprehensive field investigations and laboratory analyses show that palaeolakes, including freshmesohaline water Megalake Tengger and other semi-connected, isolated water bodies, during late Pleistocene covered an area of more than 20000 km, which is more than half of the Tengger Desert in NW China. Stratigraphic correlation and chronological evidence indicate that before ca. 42000 aBP the area was more arid. The palaeolakes started to develop around 40000 uncal. C-14 aBP but until 37000 C-14 aBP their scope, was limited. High water levels established from 35000 C-14 aBP lasted until 22000 C-14 aBP. Lake levels regressed between 22000 and 20000 C-14 aBP but transgressed from 20000 to 18600 C-14 aBP. Subsequently, water level declined further and the Megalake Tengger finally desiccated at around 18000 C-14 aBP. Megalake Tengger possessed a fresh-mesohaline water property, implying that the regional precipitation increased significantly. During the period of Megalake Tengger, the climate was warmer-humid than present. The annual rainfall was 250 to 350 mm more than that of today and the temperature was 1.5 to 3.0degreesC higher.