Abstract: Pre Sinian strata in the Yunkai area are composed of the Yunkai Group of the Qingbaikou’ an Period Jixianian Period and the Gaozhou Group Complex of the Changchengian Period.Three new lithostratigraphic units,the Huangling Formation Complex,Guantang Formation and Xinan Formation,have been established.Regionally,the Gaozhou Group Complex is equivalent to the Sibao Group in southeastern Guangxi and the Baoban Group in Hainan,and the Shawanping Formation of the Yunkai Group to the Danzhou and Shilu Groups.The Luoxia,Fengdongkou and Lankeng Formations were deposited in the Jixianian Period in the Yunkai area in the center of the rift basin.