Abstract: The sea-level change is a key factor for controlling succession of fossil communities and recog-ni tion and division of sequence stratigraphic units.In a complete cycles of transgression and regression,fos-sil communities shows periodic change of succession of the opportunistic species community,equilibrium species community and ultimate species community.The abundance,diversity,equitability and shell type of fossils have close coupling relationships with the transgressive systems tract,deposits of the condensed inter-val and highstand systems tract of the third-order sequence of sequence stratigraphy.The succession and change of fossil communities are the reflection of the change of the marine environment.Therefore,the study of fossil communities may help recognize and optimize sequences,sedimentary systems tracts and se-quence boundaries,thus providing a new approach to the accurate recognition and division of sequence stratigraphic units.