High lake levels of terminal lakes indicate warm and humid climatic conditions. Controversial views exist regarding the ages of high lake levels on the QinghaiTibetan Plateau. One view (mainly based on 14C dating) proposes that the panlake period (40~28 ka BP) or great lake period (40~25 ka BP) generally existed in the late part of the Marine Isotope Stage (MIS) 3, during which the temperatures and precipitation were probably much higher than those in the Holocene. However, another view (mainly based on Optically Stimulated Luminescence (OSL) and Useries dating) argues that the highest lake level of paleolakes on the QinghaiTibet Plateau occurred in MIS 5 and later lowered gradually. Gahai Lake and Toson Lake are located in the eastern Qaidam Basin, northeastern QinghaiTibet Plateau. Here we report quartz OSL age estimates of highstand lacustrine sediments and beach deposits to establish the lake level history for the two lakes. The results imply that the high lake stands existed at 82~73 ka, 63~55 ka, 34.4 ka and early Holocene (11~9 ka), and that the highest lake level occurred in MIS 5 in the Late Quaternary.