In the chronostratigraphy framework, the Xiayoushashan Formation of Nancan-2 well in Wunan area of Qaidam Basin can be divided into two medium base-level cycles (Class-3 sequence). The changes in sedimentary environment and base-level cycles is interactional, so the sedimentary facies and paleoecology characters are significant evidences on the cycle division. Therefore, the isochronous stratigraphic framework of Wunan area is established, the relations between base-level cycles and paleontology responses are then analyzed. com:office:office" />