The invention provides a novel method for synthesizing spherical nano-structure Ni(OH)2 through an atom economical method. According to the method, nickel, oxygen in the air and water are directly synthesized into the nano-structure Ni(OH)2 in a specific base solution, ammonium chloride is adopted as a nickel anode activator, the dissolving out and generation speed of Ni2+ of the nickel anode is substantially improved, simultaneously, ammonia water is adopted as a main complexing agent, ammonium citrate or ethylene diamine tetraacetic acid disodium salt serves as a crystallization control agent, and the spherical nano-structure Ni(OH)2 is obtained through a fuel cell type discharge reaction. The base solution can be recycled repeatedly and consumption of chemical materials is avoided to the utmost in a synthetic process.