Abstract: In the light of fossils of Tetracoralla collected from the Dacaigou Formation on the southwestern margin of the Qaidam basin, it has been verified that there exist strata equivalent to the "Longyin Formation" of southwestern Guizhou. It is proposed that the Carboniferous-Permian boundary is marked by the appearance of the Kdpingophyllidas fauna, and accordiing to the regularity of vertical distribution of its genera and species in section. three coral assemblages are established in descending order: （3） the Anfractophyllum-Nedkepingophyl- lum assemblage, （2） the Eokepingophyllum-Kepingophyllum assemblage, and （1） the Nephelophyllum-Antheria compacta assemllage. The geologic age of the Daoaigou Formation is assingned to the initial Early Permian.