<p>This paper deals with a water-hammer impregnation method previously developed as a novel approach to improve the uniformity of liquid impregnation into wood, by targeting aspirated pits and tyloses, which are known to restrict liquid flow. Our previous study demonstrated that liquid permeation was promoted by the water-hammer impacts, although the mechanism underlying this effect remained unclear. In this study, the effects of water-hammer impacts on liquid permeation, the aspirated pits and tyloses, and the collapse of wood were investigated for several species to clarify the mechanism of this promotion of liquid permeation. Several hardwood and softwood species were tested using an improved apparatus capable of generating stable water-hammer impacts. The effect of water-hammer impacts on liquid permeation was quantitatively evaluated based on the difference in water uptake with and without the impacts, while collapse was evaluated based on external dimensions. The results showed that the water-hammer impacts promoted liquid permeation without causing significant collapse in all species. Among the species examined, sugi (<i>Cryptomeria japonica</i>) and kiri (<i>Paulownia tomentosa</i>) exhibited the most pronounced promotion. Microscopic observation suggested that aspirated pit membranes in sugi and tyloses in kiri were locally removed or ruptured, providing additional flow paths for liquid permeation. Examination of the effect of hammering conditions indicated that the region affected by the impacts extended farther into the interior in kiri than in sugi. These findings suggest that liquid permeation is promoted by partial damage to aspirated pit membranes and tyloses, which depends on the species-specific wood anatomy.</p>