Objective To investigate the morphology and application of corrosion products of EW75 / AZ31 / AZ91 magnesium alloys in NaCl solution. Methods The morphologies of the corrosion products of different magnesium alloys immersed in NaCl solution for different time were analyzed, and compared with those of the traditionally chemically synthesized nanometer Mg(OH)2. Results The experimental results showed that micro- and nano-structured corrosion products with shapes of mesh, polygon star or pine needles were obtained for the three magnesium alloys after 60 h of corrosion in 35 ℃, 5% NaCl solution. Conclusion By controlling the corrosion conditions, controllable preparation of nanometer magnesium hydroxide on the surface of magnesium alloys could be realized. And compared with traditional methods, this method was simpler, more convenient and more environmentally friendly.