Felsite dykes of El-Sibai area characterized by high content of Uranium and Thorium, two types of algae were chosen to take action on biosorption of Uranium and Thorium from felsite dykes of El-Sibai area. Represented by [Pyrophyte (Sargassum detofiulum) and Rhadophyta (Ulva Lactuca)]. Felsite dykes of El-Sibai area characterized by a high content of Thorium (Th) and Uranium (U), Sargassum detofiulum and Ulva Lactuca show biosorption capacities of (81%, 89%), for U and (77%, 88%) for Th, respectively. Therefore, it was preferable to use Ulva Lactuca on biosorption due to its high sorption than Sargassum detofiulum.