Abstract： Radiolaria fossils were discovered for the first time in the lower Cambrian and middle Ordovician strata of the South China orogenic belt. They occur in argillaceous slate of the lower Cambrian Niujiaohe Formation in Pingxiang of Jiangxi Province and silicalite of the middle Ordovician Yanxi Formation in Yongzhou of Hunan Province. The discovery of Radiolaria shows that there might have existed a low-latitude sea basin of considerable scale in Pingxiang-Yongzhou area in Cambrian-Ordovician period.