The coating formed on AM50 magnesium alloy by microarc oxidation (MAO), using DC pulse power in Na(2)SiO(3) solution. The oxide coating contains a loose layer and a compact layer, the loose layer consisting of MgO, Mg(2)SiO(4) and MgSiO(3) phases and the compact layer mainly of the MgO phase. The curves of hardness (H) and elastic modulus (E) across the coating are similar, from the surface to the interior of the coating, H and E increase, and both of them exhibit a maximum value at the same depth of the coating. After MAO treatment, the mechanical properties, such as hardness and elastic modulus, can be improved, and the microstructure of the alloy substrate has not been changed.