Abstract:To study the impact of the pine wood nematode (PWN, Bursaphelenchus xylophilus) invasion on the micro-structures of Pinus massoniana and P. thunbergii ,slicing section technology was used. The results indicated that the structures showed lesion characteristics during the early period of invasion and become aggravated with the time passed. For P. massoniana, parenchyma cells became lignified and cell rupture. During the second period of invasion, periderm cells, parenchyma cells of cortex and phloem all became lignified and their contents even cambial cells also became lignified. In the later period, all cells became lignified and lots of cells rupture. However, for P. thunbergii, pathogenic characteristics were the same as that of P. massoniana, but occured later and the disease degree was lighter, which indicated the difference of resistance to PWN between two pine trees. Histopathological features at the same stage were also different, it was related to the location of invasion and the distribution of PWN in the pine trees.