Abstract: Objective To study the effect of Fe₂O₃ nanopar ticles on proliferation and apoptosis and the oxidativ e damage of RA w264.7 cells.Methods The cy to toxicity and inter vening concentration of nanoparticles were detected by MTT assays.0.24,0.48 and 0.96 mg/ml Fe₂O₃ nanoparticles suspension-inter vened macrophages were set as Fe₂O₃ nanoparticle groups,and normal saline group was set as control group.The levels of LDH activity in medium were analyzed using the reagent kits.The mitochondrial membr ane potent(MMP)and cell apoptosis rate were analyzed by flow cytometry.Results The proliferations of RA w264.7 cells were suppr essed when exposed to Fe₂O₃ nanopart icles of 0.816~3.523 mg/ml.The IC₅₀ of Fe₂O₃ nanoparticles on RAW 26417 cells was 11.76 mg/ml.The levels of LDH activity in Fe₂O₃ nanoparticle groups were higher than that of control group(P<0.05).Flow cytometry assay showed that the MMP decreased in different exposure groups and cell apoptosis rate of exposure groups were higher than that of the control(P<0.05).Conclusion Fe₂O₃ nanoparticles could cause cytotoxicity,increase cell membrane permeability and depress the activities of LDH.Fe₂O₃ nanoparticles could also reduce the MMP and lead to apoptosis in RAW 264.7 cells.