Abstract:Tongguer Formation, one of the most famous Neogene fossiliferous strata in China, is well developed in Tongguer (Tung Gur) district located in the southeast part of Erlien, Inner Mongolia. Sporo-pollen assemblage obtained is characterized by the dominont content of Qucrcoidites, Chenopodipollis, Artemisiaepollenites, and by the moderate amount of Salixipollenites, Cyrillaceaepollenites, Tricolpopollenites, along with a few of Betulaceoipollenites, Ulmoideipites, Labitricolpites, Rutaceoipollis, Graminidites, Pinuspollenites, Abietineaepollenites, Ephedripites and Polypodiisporites etc.. A comparison is made between the present assemblage and that from Shangdou-Huade Basin, Inner Mongolia, and the climatic variation tendency revealed by these assemblages is contrast with that from the oxygen isotopic records of the DSDP boreholes. The geological age of Tongguer Formation is then assigned to the middle Miocenelate Miocene boundary or the earliest late Miocene, which is a slight later than the result from the vertebrate fossils.