Abstract: Fastgrowing poplar wood was modified by watersoluble ammoniacal copper quaternary (ACQD) using vacuumimpregnating method. Mechanical and sorption isotherm performance of untreated and modified wood with ACQD, were studied in this paper. The results showed that the effects of treatment with ACQD using vacuummethod on mechanical performance of fastgrowing poplar wood was not significant. Nelson equation could describe sorption performance of untreated and modified wood with ACQD well. Antidecay modification didn’t change sorption nature of poplar wood.