Abstract: In order to study the southern boundary of the eastern plateau in China, the data of Yanshanian granite reported in the literature in the southern Anhui are collected and sorted out in this paper. The results show that, Yanshanian granites in the southern Anhui Province can be divided into early (150 ~ 132 Ma) and late (132 ~ 120 Ma) periods roughly at 132 Ma. The early granites are mainly granodiorite, monzogranite and a small number of two-mica granite, with adakite characteristics, while the late granites are mainly potassium-rich granites, belonging to A-type granite. The study indicates that the southern boundary of the eastern plateau in China is not along the lower reaches of the Yangtze River, but extends to the southern Anhui Province and adjacent areas. The "Southern Anhui Plateau" was formed around 150 ~ 132 Ma and experienced a collapse around 132 Ma, causing the boundary of the plateau to retract northward to the lower reaches of the Yangtze River. The overall collapse of the eastern plateau in China occurred around 125 Ma, but some thickened areas still remain, mainly distributed in the eastern side of the plateau, such as eastern Liaoning Province, eastern Jiaozhou Bay, northern Jiangsu Province, and Nanjing to Zhenjiang City.