Abstract: The strata of Yeyungou Formation in Dashankou section is well exposed，mainly composed of carbonate rocks and a little clastic rocks，with a thickness of 6968 m.The rock types of this section are mainly limestone which may be divided into calcirudite，oolitic limestone with continental clast，bioclastic limestone，calcarenite with continental clast，microcrystalline limestone and micrite.Yeyungou Formation mainly developed carbonate slope facies，deep water basin facies and a little carbonate open platform facies.The carbonate slope facies mainly consists of calcirudite，thinbedded microcrystalline limestone and micritic calcarenite，the basin facies is mainy microcrystalline limestone and micrite and the open platform is mostly composed of bioclastic limestone，oolite and microcrystalline limestone.Calcirudite developed in the lower part and the top of Yeyungou Formation，formed in carbonate steep slope environment which is characterized by carbonate debris flow.Yeyungou Formation is mainly composed of several cycles of carbonate open platform，slope and basin sedimentation.