[Objective] Preparation of carbon nanocapsules coating Fe nanomaterials is studied. The growth process of carbon nanocapsules is briefly discussed in term of composition and structure of precursor. [Methods] Carbon nanocapsules can be here effectively synthesized by catalytic carbonizing cellulose in hydrogen flow. The carbohydrate was carbonized in a controllable way. [Results] Transmission electron microscopy (TEM), energy dispersive X-ray (EDX), Raman spectrum and X-ray diffraction (XRD) were employed to characterizing carbon nanomaterials. A large amount of carbon cages nanoparticles with 30-50 nm diameter nanocapsules coating metal cores. The shells of the nanospheres are composed of highly ordered graphitic sheets. The encapsulated iron cores were found to be metallic and single crystalline phases. [Conclusion] Carbon-coated magnetic nanoparticles with well-developed quasi-spherical shape can be prepared from biomaterials, cellulose.