Tubular magnesium oxide (Mg0) nanocrystals were fabricated via combining ammonium sulfate leaching and precipitation method with calcined dolomite (CaCO3.Mg0) as magnesium source. The relationship between (NH4)(2)S0(4)/Mg0 molar ratio, volume of distilled ammonia and dosage of calcined dolomite and the leaching rate of magnesium were investigated, and the highest value of 96.81% for leaching rate was obtained by optimizing leaching conditions. The tubular Mg0 nanocrystals were synthesized by precipitation and calcination process, which were characterized by XRD, FT-IR, SEM and TEM. After calcination process, the crystallite size of MgO nanocrystals varies from 12.4 nm to 42.2 nm with the calcination temperature increases from 500 degrees C to 1000 degrees C. The activation energy for crystal growth of MgO nanocrystals is about 10.69 1.13 kJ/mol before 650 C, while it increases to about 27.02 +/- 0.95 kJ/mol after 650 degrees C. (C)2017 Published by Elsevier B.V.