Abstract: Excellent effects of treatment can be obtained by acetylation carried out in the liquor phase without catalysts.Dimensional stability measurements of 3 species (Finns massoniana, Lamb., Fraxinus mandshurica, Rupr. and Tilia amurensis, Rupr.) indicated: 1 ) Anti-shrink efficiencies (ASE) 60.40-86.77 per cent, 2 ) Equilibrium moisture content decreased by as much as 50.80 to 72.77 per cent, 3) After conditioning at 35 c and 50 per cent relative humidity for a week, change of moisture content reduced by 53-79 to 72-77 per cent and swelling reduced by 52.79 to 76.96 per cent.Under the treatment conditions used, it was the difference between wood species rather than the ratios between acetic anhydride and wood that made a much more important effect.The colour of the wood treated was more bright than natural. The porosity of wood was not changed.The remaining solution was analysed after the reaction had been finished. Results indicated that it still contained acetic anhydride at an amount of 20.80 to 21.60 per cent, which can be used again.