The thermally expandable microspheres were prepared through suspension polymerization with acrylonitrile (AN), methyl methacrylate (MMA) and methyl acrylate (MA) as monomers. The experimental results showed that it was possible to apply suspension polymerization to prepare the high foaming ratio and equally distributed microcapsules when water and oil phase volume ratio of 3:1, AN-MMA-MA in the proportion of 70%/20%/10% (m/m/m), and 1,4-butanediol dimethacrylate (BDDMA) as the crosslinking agents. Furthermore, the structure and property of shell and nuclear were characterized by Infrared Spectra (IR), Scanning Electron Microscopy (SEM) and Thermal analysis (TG, DTG). The structure characteristics and effective factors of copolymer coated core materials, morphologies, particle sizes, foaming temperature and ratio of microcapsules were investigated in this paper.