Populus ussuriensis has been widely used in furniture and building. However, it was easy to be decay. When it was treated by water extractive of camphor leaves, it had better effect on against decay. So it was necessary to research the preservation mechanism of it. Therefore, the water extractives of camphor leaves and the ether extractives of treated P. ussuriensis were determined by GC/MS. The results shown the main components were D-Camphor, 1, 6-Octadien-3-ol, 3, 7-dimethyl- and α-Terpineol in water extractives of camphor leaves. They were served as cardiotonic, anodyne, preservative, pesticide, so they had function of prevention. And, they also existed in treated P. ussuriensis. Therefore, the preservation mechanism was maybe known that D-Camphor, 1, 6-Octadien-3-ol, 3, 7-dimethyl- and α-Terpineol was active substance for bacteriostat. So, the water extractives of camphor leaves could be develop an environment-friendly wood preservative.