Abstract: Objective To enhance the anti-tumor immunity of macrophages by increasing iron concentration in the macrophages using nanospheres. Methods Anti-CD206 antibody-conjugated Fe3O4-based polylactic acid glycolic acid (CD206- Fe3O4-PLGA) nanoparticles were prepared with the W/O/W method. The particle diameter was measured using Malvern particle size detector, the Zeta potential was determined using Zeta potentiometry, and the encapsulation efficiency of Fe3O4 was determined using an iron determination kit. The macrophage-binding and targeting abilities of the conjugated nanoparticles were evaluated using immunofluorescence assay, and the polarization index of macrophages was determined with Western blotting and qRT-PCR. BALB/C-57 mouse models bearing subcutaneous tumors were used to verify the efficacy of the nanoparticles to promote polarization of the tumor-associated macrophages (TAMs). Results The conjugated nanoparticles had a mean diameter of 260-295 nm with Zeta potential values ranging from -19 mV to -33 mV, encapsulation efficiency of Fe3O4 ranging from 65% to 75%, and anti-CD206 conjunction efficiency of 65%-70%. Immunofluorescence assay verified the targeted binding ability of the nanoparticles with M2 macrophages. Western blotting and qRT-PCR confirmed that both CD206-Fe3O4-PLGA and Fe3O4-PLGA nanoparticles promoted the expression of TNF-α, iNOS and IL-1β (P<0.05). In the tumor-bearing mouse models, CD206-Fe3O4-PLGA nanoparticles were confirmed to promote CD86 expression in the TAMs. Conclusion CD206-Fe3O4-PLGA nanoparticles are capable of targeted binding to M2 macrophages and reversing the M2 macrophages to M1 phenotype by releasing coated iron oxide particles.