Nickel Oxide (NiO) nanocrystalline has been successfully synthesized by Ethylene Glycol (EG) route. The samples were prepared using NiCl 2 ·6H 2 O as precursor, EG as solvent and agglomeration preventing agent, and ammonium bicarbonate as precipitant. In this research, the effect of calcination temperature and precursor concentration were investigated. The experimental result showed that crystallite sizes of NiO were 4.8 nm, 9.1 nm, and 15.3 nm when the calcinations temperature was 300°C, 400°C, and 500°C respectively. It was obvious that when calcinations temperature increased, the crystallite size of NiO increased, then the calculated activation energy for NiO nanocrystalline growth during calcinations is 21.33 kJmol -1 .In the effect of precursor concentration,by using concentrations 0.25 M, 0.5 M, and 1 M, crystallite sizes increase with the increasing concentration as 17.4 nm, 15.7 nm, and 24.8 nm respectively. These result implied that crystallite size of NiO powder can be controlled not only by calcinations temperature but also controlled by precursor concentration.