In this study,a novel method was used to prepare well-separated and spherical tricobalt tetraoxide(Co3O4)nanosized particles.The overall process involves three steps:preparation of insoluble carboxyl-containing grafted starch copolymer(ISC),formation of precursor(ISC-Co),decomposition of ISC-Co,and phase transition of Co304 nanoparticles.The Infrared spectra used for ISC and ISCCo are discussed.The decomposition of the precursor was studied by thermogravimetric-differential thermal analysis,the crystalline phase was characterized by x-ray diffraction,and the size distribution and shape of particles were observed by transmission electron microscopy.