Abstract: The contents of zinc in milk powder of many brands were determined by atomic absorption spectroscopy, the experiment conditions such as composition and proportion of mixed acid used in the digestion of milk powder by dry method were researched. The optimum condition for its sample treatment was with nitrate acid-perchloric acid （4 ＋1）as dissolving acid and 1 mol/L hydrochloric acid as constant-volume acid. The relative standard deviation of determination results was smaller than 2 %.