Abstract: s:The longitudinal variation of main chemical compositions in the heartwood and sapwood of Chinese fir and Poplar×euramaricana cv.I-72/58 were studied. The holocellulose, α-cellulose, lignin, acid-soluble lignin, and the ratio of cellulose to lignin were investigated. The results showed that the contents of holocellulose and cellulose in both Chinese fir and Poplar×euramaricana cv.I-72/58 were higher in the sapwood than in the heartwood, but differet in logitudinal direction of the woods.The variability pattern for the content of hemicellulose in the sapwood and the heartwood of both Chinese fir and Poplar×euramaricana cv.I-72/58 was different; the content of lignin for Chinese fir was higher in the sapwood than in the heartwood, the content of lignin became lower in the sapwood and increased in beginning then stepped up with the tree part being higher.The variability pattern for the content of lignin in the sapwood and the heartwood of Poplar×euramaricana cv.I-72/58 was also different.The content of acid-soluble lignin became lower in the sapwood and heartwood of both Chinese fir and Poplar×euramaricana cv.I-72/58 with the tree part being higher.The content of acid-soluble lignin was higher in the sapwood than in the heartwood for Chinese fir, but the content of acid-soluble lignin was higher in the heartwood than in the sapwood for Poplar×euramaricana cv.I-72/58.The variabilities for the ratio of holocellulose to lignin follow different patterns in the longitudinal direction.