Chitosan is a natural and renewable polymer without toxic and pollution to human beings and environment and can be used to improve effect of surface dyeing for wood.Lightfastness of wood pre treated with chitosan and then dyed was studied in this paper.Six wood species were pre treated or untreated with chitosan and then all dyed with one acid dye.One wood species was pre treated or untreated with chitosan and then all dyed with 4 kinds of acid dyes.The results showed that lightfastness of pre treated wood was better than that of untreated one.