In this study, spruce sapwood was administered an alkaline enzyme treatment to improve the flow of wood liquid so that more preservative chemicals could be injected. Spruce wood is recognised as a refractory wood species. Pit membranes play an important role in liquid flow. In this study, an alkaline pectinase enzyme was applied to remove the pectin layer on the torus of the pits and margo. After enzymatic treatment, the pectin layers on the pit membrane were removed. When samples were investigated by both scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP), it was evident that pit membranes were destroyed and the permeability increased. In addition, no noteworthy weight loss was observed.