Abstract:Chemical compositions of Pine wilt diseased wood and sound wood have been researched.It was found that there is no notable difference between soundwood and diseased wood in major componentcellulose, hemicellulo and klason lignin,but content of phenealcohol and ethylether extractive substantially decrease.After pine wood is attacked by Bursaphelenchus xylophilus, the decrease in amount of thylethen extractive of diseased wood is a dominant characteristic.Otherwise there are some difference in chemical components of thylethen extractive and PH value of wood between sound wood and diseased wood. The sound wood and diseased wood are distinguished by colour reaction used proper indicator.