A novel method, combining polymerization and pyrolysis of single precursor on graphite sheet, has been developed to synthesize monodispersed boron carbonitride hollow spheres in large-scale. The products have hollow architectures (2-3 mu m in diameter) with nano-pores on the spherical walls and a composition of B0.23N0.19C0.58. The products exhibit the minimum reflection loss of -42.5 dB at 12.6 GHz (the effective reflection values are obtained in a very wide range of 3.4-17.3 GHz) suggesting a new and high quality microwave absorbent. (C) 2015 Published by Elsevier Ltd.