A calcium phosphate coating was prepared on the surface of micro-arc oxidized magnesium by a chemical method. The microstructure evolution of the coating was characterized by X-ray diffraction, Fourier-transformed infrared spectroscopy and scanning electron microscopy. The results showed that Ca(10)(PO(4))(6)(OH)(2) (HA) was firstly formed on the surface of micro-arc oxidized magnesium, followed by flake-like CaHPO(4)center dot 2H(2)O (DCPD). The solution pH and Ca(2+) concentration had intense influence on the formation of calcium phosphate coating. Acidic Ca(2+) enrichment solution was favourable for HA formation on the surface of micro-arc oxidized magnesium. High concentration of HPO(4)(2-) and low concentration of Ca(2+) in acidic solution improved the formation of DCPD coating. (C) 2011 Elsevier B.V. All rights reserved.