Abstract: Eleven years old Pinus massoniana from 9 half-sib families in Duyun clonal seed orchard were studied on the genetic variation of the wood samples in 4 wood chemical components, including basic density, ash content, 1%NaOH extract and cellulose content. The results indicated that there were significant differences between basic density and 1%NaOH extract. There were 4 types of longitudinal and radial variation in wood basic density and its chemical composition. In vertical, ash and cellulose of the tree tops, where the ash content was the highest and the cellulose content is lowest, were significantly different from those in the middle and basal parts. Therefore, the tree tops are unsuitable for pulpwood. The radial middle wood density was closest to the average density levels of families. The difference of other indexes were not significant with ash exception, and the average value is relatively close at radial direction. Ash content was positively correlated with basic density, and we can make a positive selection of ash through the basic density.