Arsanilic acid (ASA), an organic-arsenic veterinary drug used widely, has greatly attracted attention due to its potential threats. We report the nanocomposites of the α-Fe2O3 nanoparticles growth on reduced graphene oxide (rGO) by a one-pot method. The α-Fe2O3 nanoparticles are densely covered on the surface of rGO according to the observations of transmission and scanning electron microscope. The adsorptive capacity (357.4±11.2mg g-1) of the Fe2O3@rGO nanocomposites for ASA, which was more than the sum of adsorptive capacities of the pure α-Fe2O3 nanoparticles and rGO, revealed a remarkable enhancement due to the synergetic effect of multiple interactions and the good dispersion of α-Fe2O3 nanoparticles with more active binding sites in the Fe2O3@rGO nanocomposites. The adsorption equilibrium of ASA onto the Fe2O3@rGO nanocomposites was achieved for 60 min, and the adsorption of ASA was dependent of pH and temperature, and independent of the concentration of humic acid ranging from 0 to 20 mg L-1. After five cycles of adsorption-desorption, the adsorptive amounts of ASA by the regenerative sorbent still retained 85% of adsorptive amount by the fresh sorbents. The adsorption process of ASA can be described by the Langmuir and the pseudo-second-order equations and is exothermic and spontaneous according to thermodynamic analysis.