Abundant sporo-pollen fossils were found in cores from the Chang 8 and Chang 7 members of the Yanchang Formation in the southwestern Ordos basin, NW China. The assemblage of Chang 8 member was denominated by Aratisporiteas-Punctatisporites, and the assemblage of Chang 7 member as Asseretospora-Walchiites. Their charae teristies are similar to those of the assemblages of the Tongchuan Formation and the Yanebang Formation in the southeast Ordos basin, respectively. Their geological ages are Ladinian of late Middle Triassic and Carnian of early Late Triassic respectively. The sporo-pollen and their ecological distributions in these members suggest the paleocli mate of the eastern Gansu Province in the Middle and Late Triassic was warm and wet, under a temperate to subtropi cal zone. The wetter paleoenvironment during the Chang 8 and Chang 7 sections deposited in eastern Gansu Province large-scale lake transgression was happening, with the largest lake.