Carbon-coated Fe3O4 porous particles were synthesized with phenolic resin as a carbon source using impregnating pyrolysis. The magnetic property, phase structure, pore structure, and surface morphology of the pyrolysis products were characterized by vibrating specimen magnetometer, X-ray diffraction, Brunauer–Emmett–Teller (BET), and scanning electron microscopy, respectively. Also, the adsorption properties of iron (III) ions on Fe3O4@C as well as pure carbon, including adsorption isothermal, kinetics, and pH effect, were investigated. The results showed that the size of synthesized Fe3O4@C particles ranged from 10 to 50 μm with micro-meso pores sized below 5 nm. The main phases of Fe3O4@C were magnetite, graphite and amorphous carbon. The adsorption kinetics of iron (III) ions on Fe3O4@C could be expressed by the pseudo-second-order kinetic model and the adsorption isotherm was fitted by a Freundlich model. Nano-Fe3O4 had synergism to porous carbon on the absorption of iron (III) ions.