A facile and low-toxicity approach was proposed to synthesize a new magnetic adsorbent(Fe3O4@PDA@RGO) to remove methylene blue(MB) in water samples.Dopamine could directly adhere to Fe3O4 by one-step self-polymerization reaction，which serves as a reducing agent as well as a coupling agent for the assembly of reduced graphene oxide(RGO).The synthetic progress involves no additional chemicals and thermal treatments.Transmission electron microscope(TEM)，Fourier transform infrared spectroscopy(FTIR)，X-ray diffraction(XRD) and Raman spectroscopy were used to characterize the magnetic composite nanoparticles.The results demonstrated that Fe3O4@PDA@RGO has a strong magnetism(37.8 emu?g-1) and exhibits a high adsorption capacity to MB(98 mg?g-1).The adsorption of MB on Fe3O4@PDA@RGO is pH-dependent and favorable in basic solution.The adsorption behavior of MB on Fe3O4@PDA@RGO could be described by the pseudo second order kinetics model and Langmuir isotherm.Furthermore，the as prepared adsorbent can be easily recovered and reused at least ten times due to its high magnetization and stability.