Particle-like MgO powders were first prepared using LiCl as reaction medium, MgCl2·6H2O and CaCO3 as reaction materials. Soaked them by PEG and PEG-EDTA solution, different Mg(OH)2 precursors were formed, which morphologies were fiber-like via PEG and tetrahedron-like via PEG-EDTA . Re-heated at 600 , Mg(OH)2 was decomposed to MgO. Decomposed by fiber-like Mg(OH)2, MgO powders were chain-like, with 0.1-0.3 µm in diameter and 20-100 in length-to-width ration. On the other side, decomposed by tetrahedron-like Mg(OH)2, MgO powders were layer rock-like with vertex defected, which brim was up to 1.5 µm in length.