Magnetic Fe3O4 nanoparticles were prepared to immobilize lipoxygenase. The influence of factors on the enzyme activity of free enzyme and immobilized lipoxygenase was investigated. The results showed that the particulates were black short rod particles by TEM, and the mass of enzyme immobilized on the composite carrier was about 6.0%; the optional temperature for free enzyme and immobilized lipoxygenase was the same of 30 ℃; the optional pH value for free enzyme was 8.0, for immobilized lipoxygenase 9.0; The activity of the free and immobilized lipoxygenase showed a maximum activity when H2O2 concentration reached 14.0 g/L and 8.0 g/L,respectively. Under the optimum conditions, the activities of free and immobilized enzyme were 3.95×105 U/mL and 9.40×105 U/g, respectively.