Under atmospheric pressure and a pressure of 0.6 MPa，the fast-grown poplar wood was treated with a water-soluble ACQ preservative at concentrations of 0.1%，0.5% and 1.0%. The content of ACQ in wood and the depth of preservative penetration were examined. The results showed that the content of ACQ in wood was increased significantly with the increase of the preservative concentration. The requirements of Chinese preservation standards (grade C1) were met when the wood was treated with 1.0% ACQ preservative under atmospheric pressure for 72 hours. The penetration depth was negatively correlated with preservative concentration. With an identical concentration，no significant differences in penetration were found among the longitudinal, radial and tangential directions. Compared with the atmospheric pressure, the penetrations of poplar in longitudinal，radial and tangential directions were significantly increased when the treatments were carried out under the pressure of 0.6 MPa.