Abstract: In this paper, the growth and attack pattern of the white-rot fungus Coriolus versicolor NFU 008 and the micromorphological and ultrastructural changes in rotting wood popuhts deltoides were studied by transmission electron microscope (TEM). The results show that NFU 008 not only has great ability to degrade lignin, but also has a strong selectivity. In the early stage, it preferentially degrade lignin of cell walls and cause partial separation in cell corners and the compound middle lamella of fiber cells. Besides, the extracellular slime around hypha plays an important role in wood rotting. It is integrally associated with the extracellular metabolites of the degradative fungus. The results also show that the gelatinous layers of gelating fibres have strong resistance to C. versicoiar and they remain almost intact during the period of rotting.