A novel core-shell bio-adsorbent was fabricated by using biological materials for removing methyl orange (MO) from aqueous solution. The structure characteristics results of scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), thermo-gravimetric analysis (TGA), vibrating sample magnetometer (VSM), and Brunauer–Emmett–Teller (BET) shows that Fe3O4-CS-L has been successfully prepared. The effects of contact time, pH, temperature and initial concentration were explored. The results suggested pH was a negligible factor in adsorption progress. Kinetic studies showed that the experiment data followed pseudo-second-order model. Boyd mode suggested that external mass transfer showed a rather weak rate control for MO adsorption onto Fe3O4-CS-L. Equilibrium studies showed that isotherm data were the best described by Langmuir model. The maximum adsorption capacity of MO estimated to be 338.98 mg/g at 298 K. Moreover, the adsorption capacity of Fe3O4-CS-L can keep about 74% in the fifth adsorption–regeneration cycle. Thus, the Fe3O4-CS-L could be a kind of promising material for removing MO from wastewater.