A method using capillary gas chromatography for simultaneous determination of linolenic acid,ARA,EPA and DHA in milk powder was developed and heneicosanoic acid methyl ester was selected as the internal standard substance.The samples were firstly saponified and methylated with KOH-CH3OH.These methyl esters were then analyzed with GC by Internal standard method.The linolenic acid,ARA,EPA,DHA and internal standard substance were separated from each other.There were good linear relationships between their concentration and their peak area,and the correlation coefficient were more than 0.998.The recoveries for adding standards were 95.4% ~ 104.7%,and the coefficient of variation were 2.168% ~ 4.368%.The limits of detection were 1.0mg/100g.The method is simple,fast and accurate for the determination of linolenic acid,ARA,EPA and DHA in a lot of milk powder samples.