Abstract:According to the bioassays of the two-year needles of damaged and undamaged Pinus tabulaeformis Carr. and the situation of Dendrolimus spectabilis Butler larvaes growth, development and reproduction fed on these two kinds of leaves, it was found that the chemical components in the leaves of damaged pine had significant changes. The concentrations of isoleucine, methionine, tyrosine, lysine increased, total amino acids and other several amino acids descended. The concentrations of soluble sugar, crude fat, tannins,alkaloid and the ratio of total sugar to total amino acids all rises. There were large changes in fatty acids, phenenes, terpenoids and mineral elements. The larvae fed on leaves of damaged trees had a 33.5% lower in herbivory,a 10% growth in mortality, and fecundity dropped. Damaged P. tabulaeformis showed a significant induced chemical defenses.