Iron oxide/tin oxide composites were synthesized by a simple hydrothermal method using Fe3O4 nanoparticles as the precursor.Two kinds of Fe3O4 were used as the precursor.Fe3O4 particles and sheets were prepared by hydrothermal method and microwave heating method,respectively.Their morphology,size and structure were investigated by X-ray powder diffraction(XRD)and scanning electron microscopy(SEM).Thermogravimetric analysis(TG)and differential thermal analysis(DTA)showed Fe3O4 nanoparticles have different thermal stability.The thermal property of Fe3O4 precursor affects the final phase and morphology of the composites.High thermal stability of Fe3O4 is favor of the formation of Fe3O4/SnO2 composites.While easy oxidation of magnetite sheets led to the formation of α-Fe2O3 /SnO2 composites.The mechanism for the formation of iron oxide/ tin oxide composites was investigated.