Abstract: Sugars and amino acids of bamboo twigs damaged by Hippota dorsalis (Stal) are determined by HPLC method. Results show that total sugars and soluble sugars decrease with the injury increases. The contents of their components, such as sucrose, glucose and fructose, decrease at different degree.Free amino acids sharply increase with damage increases, among six-year-old bamboos, content of amide increases nearly 32 times, which makes up half of the total free amino acid; ARG grows up from zero to 46.49mg/100g after severe damage. LYS also increases 37 times among two-year-old ones.Total amino acids also have a marked rise after proteolysis treatment, but they have reached the highest level before severe damage comes. The total content increases 1.7 times while ARG goes up 5 times more than the contrast.The changes of different direction in nitrogen and sugars are a kind of reaction of plant to the infestation of the insect, which causes disorder of sugar and nitrogen metabolism among infested bamboos.