Abstract: The stratigraphy and lithology are discussed for the early Emsian Ganxi Formation within the Baishi-Goujia klippe in central Longmen Mountains,Sichuan.Two ecostratigraphic units including the Anetoceras-Plectodonta community and Dicoelostrophia-Eosophragmophora community have been identified for the Ganxi Formation for the first time.The emphasis is placed on stratotype section,biology,abundance,ecology,living styles and habits of individual communities.The results of research show that the study area may be assigned to deep-water shelf to deep-water basin environments during the early Emsian.This new explanation has provided new evidences for the interpretation of the nature and evolution of the Devonian sedimentary basins in the Longmen Mountain area.