A total of 42 samples from the Lake Bayan Nuur sediment core were studied for chironomid analysis . Treatment 66 of sediment samples for chironomid analysis followed the standard techniques described 67 in Brooks et al. (2007, https://edoc.unibas.ch/67001/). Subsamples of wet sediments were deflocculated in 10% KOH, heated to 70 oC for 10 minutes by adding boiling water, and left for another 20 minutes. The sediment was passed through stacked 225 and 90 µm sieves. Chironomid larval head capsules were picked out of a grooved Bogorov sorting tray under a stereomicroscope and were mounted in Hydromatrix two at a time, ventral side up, under a 6 mm diameter coverslip. Chironomids were identified as the highest taxonomic resolution based on Brooks et al. (2007). Information on the ecology of chironomid were used to reconstruct past paleoecological situation in the lake.