Nickel oxide (NiO) is a promising material extensively used in catalysis, electrochemical capacitors, etc.So far, many researchers have demonstrated the synthesis of nickel oxide nanomaterials with various morphologies, but NiO nanoparticles with millet-like structure is not reported yet.In the present work, we will report the synthesis of uniform and well dispersed millet-like NiO nanoparticles by a hydrothermal and post-treatment method without adding any surfactant.