Abstract: Fe3O4 nanopowders used in artificial muscle drived by magnetic field were prepared by chemical co-precipitation.Orthogonal tests were carried out to obtain the optimum preparation parameters.Characterization was also performed using X-ray diffraction,transmission electron microscope,vibrating sample magnetometer and so on.The average size of the prepared Fe3O4 nanopowders was 9.7 nm,and saturation magnetization intensity was 60.9 A·m2·kg-1,and they possessed superparamagnetism.Appearance of Fe3O4 nanopowders was smoother than that of analytical reagents Fe3O4 used for artificial muscle drived by magnetic field.And Fe3O4 nanopowders can be dispersed more symmetrically than those of analytical reagent Fe3O4.