Features such as lightweight and inexpensive of magnesium, increasing use of in various industries. But its impatience corrosion, it limit many of the functions. Therefore, using the micro-arc oxidation (MAO) to improve it. Appearance is also more and more attention of the commercial demand. In this study, using micro-arc oxidation on the AZ31 magnesium alloy sheet and reactive dyes successfully dyed in the micro-arc on the magnesium alloy sheet. But it show poor light fastness. It can not requirements of industry exposure in irradiation200 hours. This experiment to investigate the light fastness of different dyeing conditions, resistant to sunlight then proceed to improving the handling. Inferred from the results, in the pH12 Temperature70 ° C the concentration of 3% can upgrade from 50 hours to 200 hours by coating HS-670 A,B plus Eversorb AQ1. And best △ E value of 4.06. For the best conditions for improving the resistance to sunlight.