| In this paper, through the inoculation on the tree planted in a net room and inoculation on the branches in cages, using the amounts of oviposition, hatching rate of larvae, and survival rate of larvae as resistance index, the relative resistance of 6 poplar clones was studied. The resistance from high to low is P.tomentosa p Xeuramericana cv. iqin-J p Xeuramericana cv. iqin-2 P.deltiodes cv. hanhaiguannens is P X euraericana cv . -214 P.Canadensis. Six clones tested were divided into three groups using method of systematic cluster analysis. Genetic variation of wood basic properties and tree growth was analyzed. Through the comprehensive judgement on resistance to A.Glabripenni, growth, stem form and genetic variation of growth and wood basic properties, the new clones including pXeuramericana cv. iqin-1and pXeuramericana cv. iqin-2 was sifted as improved poplar clones with high resistance to A. glabripennis, fast growth and fine wood properties. Through the observation and measure of the morphology characteristics and dissection structures, water contents, components and content of nutrient substances and substances from the secondary metabolism and the analysis of the harmful caused by A.Glabripennis, it is concluded that: 1) The difference of he morphology characteristics and dissection structures of trees is foundation of different resistance of poplar clones to A.glabripennis The insect resistance of tree is influenced by several factors, such as the thickness, roughness and intense of bark, lenticel size, content of cellulose, lignin and ash. The resistance of poplars closely related to the number of vessel, rays?width, radium of Iignified cell and wall thickness of sclereids, but the former two factors are positive and the later two negative to resistibility of tree. 2) The poplar resistance to the insect bears no relation to the inorganic chemical components in poplar bark and oxlyn. 3) Water contents of the branches in xylem are related to the resistance of treesbut which in phloem have nothing with their resistance. There is no correlation between the content of soluble sugars and the resistance of trees. But the content of reductive sugars and the ratio of reductive sugar to soluble sugar is lower in the more resistant clones. Although different amino-acid varied differently, their vary trend is coincide with the damage caused by A. glabripennis. In other words, the higher of the components and contents of anino-acid of trees is, the more serious damage is. There is a certain correlation between the content of Aspartic acid, Glutamic acid, Asparagine, Serine, Glutamine, Alanine, Arginine, Lysine, Vail ne and the harmfulness of A. glabripennis. 4) Tannin is a distinct restrain to A.glabripennis and whether a tree is damaged by A.glabripenni is directly related to its tannin content. But the interrelated coefficient between the contents of tannin in xylem is higher than that in the phloem. The relation between the components and Contents of phenol constituents and the resistance of tree is complex, but basically the resistance to A.glabrpennis is sufficiently high with a higher proportion of phenhic compounds contained in the tree. Different phenol has a different characteristic on the relationship with harmfulness of A.glabripenni, Phenylacrylic acid and Coumaric acid found only in immuned clones P.tomentosa. Phydroxybenzoic acid and Saiicylic acid have less correlation with resistance of popla. Phenyl~ Ferulic acids Catecho...
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