The effect of nitrogen application rates on dynamic change law of tuber protein and starch synthesis of potato was studied in field experiments.The results showed that protein content of tuber also increased gradually from 63 to 91 days after sowing with the increase of nitrogen amount,but after that in 120 kg.hm^-2 nitrogen treatment it decreased rapidly.Excessive nitrogen fertilizer was not favor to the transformation of soluble sugar to starch.The starch content of potato tuber was 61.92～66.91 g.100 g^-1.DW at harvest.Excessive nitrogen fertilizer was not favor to the starch accumulation in tuber and the amylase relative content increase at later stage of potato growth.