The fungus Bovista plumbea immobilized on -Fe2O3 nanoparticles is shown to be a novel sorbent for magnetic solid-phase extractions of U(VI) and Th(IV). The biosorbent was characterized by FT-IR, SEM, and EDX. The effects of pH value, flow rate and volumeof sample, amounts of biomass and support material, eluent type, foreign ions and repeated use of the sorbent on extraction efficiency were investigated. The sorption capacities are 41 and 44mgg(-1), respectively, for U(VI) and Th(IV). The results indicated that B. plumbea immobilized onto -Fe2O3 nanoparticles can be utilized as a novel material for the preconcentrations of U(VI) and Th(IV) in certified materials and in spiked tap, river and lake waters.