Abstract: <P>Two kinds of ferroferric oxide (Fe3O4) nanocomposites namely the active carbon/ferroferric oxide (AC/Fe3O4) and carbon nanotubes/ferroferric oxide (CNTs/Fe3O4) were prepared by homogenous precipitation method in order to improve catalytic activity and stability of Fe3O4 nano-particles.Composite particles were characterized by the means of scanning electronic microscope (SEM),X-ray diffraction (XRD),and thermogravimetic analysis (TGA) and their electrochemical properties were investigated.Results showed that the obtained Fe3O4 particles had high purity and were well distributed in the particle size range of 40~100 nm.After ultrasonic treatment,CNTs/Fe3O4 composite was more stable than AC/Fe3O4 composite.Fe3O4 particles in CNTs/Fe3O4 composite were smaller than that in AC/Fe3O4 composite.Both composites had improved discharge capacity and stability of LaMgNi4 alloy.</P>