The lack of outcrops has limited biostratigraphic studies in the Yingen- Ejin basin. Also controversial is the stratigraphic division of drill cores and the corresponding age of oil and gas reservoir, if they belong to Mesozoic or Late Paleozoic. Pollen analysis was carried out to the bottom part of MED- 1 core samples from Wuzhuer depression, western Yingen- Ejin Basin to provide palynological evidence for their stratigraphic correlation. According to the variations of the sporopollen taxa and their percentages, two palynological assemblages were recognized, the Osmundacidites- Deltoidospora- nonstriate bisaccate assemblage and the Classopollis- Cyathidites- Quadraeculina assemblage. In the first assemblage, the proportions of gymnosperms and ferns are close to equal. The nonstriated bisaccate taxa are diverse and abundant, while the striate bisaccate pollen grains only appear sporadically. Fern spores are dominated by Osumundacidites, with the frequent appearances of Lycopodiumsporites, Deltoidospora, Neoraistrickia etc. Most of these taxa are common in Jurassic. The geological age revealed by the first palynological assemblage should be middle to late Early Jurassic, and the palynomorphs indicate a warm and humid climate at that time. Among the second assemblage, Classopollis becomes predominant, and both Quadraeculina and Cyathidites show an increase compared to the last assemblage. No typical taxa of Cretaceous appear in this assemblage. The geological age should be assigned to late Middle Jurassic, and the climate turned hot and dry during this period. According to the characteristics of the sporopollen assemblages, the strata previously designated as Upper Permian on the basis of Estherians fossils was redefined to be the Middle- Lower Jurassic, thus providing new paleontological evidences for the stratigraphic correlation in Yingen- Ejin basin. The revised geochronology and stratigraphy of Jurassic are well correlated in North China, and consistent with the evolution from coal rocks in humid and warm settings to eolian deposits of extremely hot environments.