Synthesis of Fe3O4 nanoparticles have attracted considerable attention due to their desirable specifications. In this study, Fe3O4 nanoparticles was firstly synthesized by the chemicals co-precipitation method, and then were modified with chitosan biopolymers. The effectiveness of modified Fe3O4 was studied for removal of chromium from synthetic wastewater. The parameters evaluated in this study including pH, chromium(VI) initial concentration, contact time and modified Fe3O4 concentration. Characteristics of the synthesized Fe3O4 nanoparticles were analyzed using SEM, XRD, and TGA techniques. The best removal efficiency (83%) was achieved at pH=2, contact time=15 min, Fe3O4 dose = 0.75 gr/L and chromium(VI) initial concentration = 50 mg/L. The experimental equilibrium data was most consistent with the Langmuir model. Correlation coefficient (R2) values for Langmuir isotherm were 0.95 and 0.96 in linear and nonlinear methods respectively. Absorption capacity was also about 39.61 mg/g. The results showed modified Fe3O4 nanoparticles have a large application performance for chromium removal from wastewater.