Abstract: Nihewan Basin,located in Hebei Province of Northern China,possesses thick Quaternary sedimentary records,abundant fossils and artifacts,and represents a place of the earliest human presence in north East Asia.However,there have been limited absolute dating methods applied on ancient Nihewan lacustrine sediments.In this study,optically stimulated luminescence(OSL)dating technique was employed to date eight samples which were collected from the uppermost parts of the lacustrine sedimentary sequences and overlying loess-paleosol deposit at Haojiatai(40°13'01.75"N, 114°38'00.8"E),Hougou(40°13'26.4"N, 114°40'48.6"E),Hongya(40°08'03.2"N, 114°39'08.7"E),from the upper lacustrine sediment and the lower part of Hutouliang section(40°09'55.5"N, 114°40'53.6"E).The geomorphological evolution of Nihewan Basin was discussed.Medium-grained(45~63μm)quartz and polymineral fraction were extracted and used for equivalent dose estimation.Quartz OSL signals of the samples encountered the problem of saturation using single-aliquot regenerative-dose(SAR)protocol.Recent studies have identified that infrared stimulation of feldspar at elevated temperature can reduce the laboratory fading rates in the blue region of the spectrum,so the post-IR IRSL SAR protocol with higher saturation dose and less fading(Buylaert et al.[63],2009)was applied for age determination.The samples were preheated to 250℃,IR stimulated at 50℃ and post-IR IRSL stimulated at 225℃ for the natural/regenerative dose and test dose.Anomalous fading of the post-IR IRSL signal was corrected using Huntley and Lamothe[58] fading correction model.The results showed that anomalous fading-corrected ages of the uppermost lacustrine sediments at Haojiatai and Hougou were 418±25ka and 363±14ka,and corresponding overlying units were 131±5ka and 180±5ka,respectively.The corrected age of the sample was 401±26ka at Hongya's top layer of lacustrine sediment. For the samples at Hutouliang,the fading-corrected age of the uppermost lacustrine sediment was 270±11ka,and the value of its lower sample was 322±18ka showing an increasing trend.Based on OSL dating results we show that there exists a sedimentary hiatus at the top of the lacustrine sediment,and the degree of erosion and weathering are different at different regions.The present uppermost lacustrine sediments do not represent the top deposit when the lake disappeared.It is critical to understand geomorphological evolution and establish an accurate chronological framework in Nihewan area.