摘要The nano-magnetic ferrofluid was prepared by chemical coprecipitation and its acute toxicology was investigated. The effective diameter (Eff. Diam. ) of the magnetic particles was about 19.9 nm, and the concentration of the ferrofluid was 17.54 mg/ml. The acute toxic reaction and the main viscera pathological morphology of mice were evaluated after oral, intravenous and intraperitoneal administration of the nano-magnetic ferrofluid of different doses respectively. Half lethal dose ( LD50 ) ＞ 2104.8 mg/kg, maximum non-effect dose (ED0) = 320. 10mg/kg with oral; LD50 ＞438.50 mg/kg, ED0 = 160.05 mg/kg with intravenous route; and LD50＞1578.6 mg/kg, ED0 =320.10 mg/kg with intraperitoneal administration. Degeneration and necrosis of viscera were not found. So the nano-magnetic ferrofluid, ofwhich toxicity is very low, may be used as a drug carri-er.