The effect of calcination temperature of Mg(OH)2 on the green density and densification of MgO was investigated. It was observed that the impure magnesium hydroxide powder showed a higher crystallization rate while it had a lower tendency of agglomeration between periclae crystallites, as compared to that of the pure magnesium hydroxide powder. In the case of calcination of the powders under 85$0^{circ}C$, the impure powder showed the higher green and sintered density. In spite of higher green density upon the calcination over 100$0^{circ}C$, the impure powder showed the lower sintered density, caused by exaggerated growth of the periclase crystallites. The highest sintered densities in the both powders were obtained at the calcination temperature of 100$0^{circ}C$. And the green density was inversely proportional to the sintered density at the calcination over 100$0^{circ}C$.