The aim of this paper is to prepare Fe3O4 nanoparticles and study its immunotherapeutic effect as adjuvants on mice H-22 live cancer. The Fe3O4 nanoparticles were prepared by chemical co-precipitation route. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Energy Dispersive Analysis (EDS) were used to characterize Fe3O4 nanoparticles. The Fe3O4 nanoparticles were compared with the common alum adjuvants for its ability to induce immunity to inhibit tumor growth rate by prophylactic and therapeutic studies. Results indicated that Fe3O4 nanopaticles adsorbed autovaccine took great advantages over the common alum adjuvants after subcutaneous injection, raised the mass inhibitory rate of tumor, boosted the activity of cytotoxicity and enhanced the level of IFN-gamma cytokine. Thus, we concluded that Fe3O4 nanoparticles as adjuvants had great potential for enhancing anti-tumor immune response.