Abstract: A comparison of radioactivity levels in the coastal sediments and plants between the Great Wall and Zhongshan Stations in Antarctica and the four seas(i. e. the Pohai Sea, Huanghai Sea, East China Sea and South China Sea)in China shows that in general the radioactivity levels in the coastal sediments and plants in Antarctica are lower than those in the four seas in China. The contens of the total β in the sediments decrease from higher to lower in amount in the order of East China Sea, South China Sca. Pohai Sea. Huanghai Sea and the Great Wall Bay in Antarctica succesively, but the contents of ~(238)U, ~(232)Th, ~(226)Ra, ~(40)K and the total β in marine plants decrease from higher to lower in amount in the order of Daya Bay in the South China Sea, Hanzhou Bay in the East China Sea and the Great Wall Bay in Antarctica successively, The results show that the contamination levels of radioactivity, espccially the artificial radioactive contamination in the Antarctic coastal area are far lower than those in China Coastal area, with the remarkable exception of ~(137)Cs.