Acid dye and reactive dye were applied to veneer from Ussuri Poplar and birch respectively;NaOH solution was used as a pretreatment reagent.The pH and buffering capacity of the dyed wood were determined to compare with that of the plain wood.The results demonstrated that the effects of NaOH solution pretreatment and the dyeing process on pH and buffering capacity were similar for the two types of wood.The dyeing process resulted in a small increase of the pH of the wood,but a distinct decrease of the acid buffering capacity.The pretreatment with NaOH solution increased the pH of the wood significantly,and the acid buffering capacity of the wood also increased during the same process.The acid buffering capacity of the Ussuri Poplar decreased significantly by either dyeing directly or dyeing after pretreating with NaOH solution.The acid buffering capacity of birch veneer decreased by dyeing directly and increased by dyeing after pretreating with NaOH solution.