Lower Paleocene foraminifer fossils were first found by the author in the Tuylok Formatior. in the western part of the Tarim Basin. They include 7 ger.era and 4 species, which are quite different from the forms of the Upper Cretaceous. The present study shows that foraminfers of the Tuylok Formation are very similar to those from the Tertiary of Europe, North America ar.d Russia. The age of the Tuylok Formation, therefore, can be determined to be Early Paleocene, i. e. the Danian, rather than the Late Cretaceous as was considered before.Five foraminiferal assemblages are recognized ir, the Paleocene of the Kuzgongsu section and Artash section, which are from the bottom upwards as follows;1.the Cibicides-Cibicidoides assemblage2.the Spiroplcctammina-Textularia assemblage3.the Lagenammina-Haplophragmoides assemblage4.the Discorbis-Globigerina-Globorotalia assemblage5.the Nonionellina-Anomalina assemblageThe Paleocene can be divided into three formations, namely in ascending order: the Tuylok Formation, the Artash Formation and the Qimugen Fornation, based on new evidence of foraminiferal fossils and geochemical and paleoclimatic anomalies between the Tuylok Formation and the underlying Ygezya Formation (i. e. the Cretaceous-Tertiary boundary found in this region).