Abstract: Natural durability of poplar wood is very low.The samples of 3 species (Populus deltoides cv."Harvard"(ex.1-63/51),Populus euramericana cv."San Martino"(ex.1-72/58),Populus tomentosa Carr.)were exposed to wood destroying fungus (Lenzites trabea Pers.ex Fr.) for a month and a half in the standard soil block test.The results indicated:1) The mean weight lost of untreated solid wood was around 40 percent,but plywood's about 35 percent that was slightly lower than the wood.2)The mean weight lost of poplar ply wood was threefold as large as ash's and bass's.Therefore,it is very importance for improving the durability of the poplar wood which used as raw material of plywood. Acetylation of poplar veneer in the vapor phase with anhydride has been carried out by using potassium acetate as catalyst and D.M.F.as swelling agent. Acetylation is a effective treatment of nontoxic type against biological deterioration.Before or after decay testing,the weight of the acetylated plywood is much the same.It shows that the acetylation of veneer can bring about marked improvement in durability of poplar plywood.