Abstractcharacteristics of differentiated xylem cells of the fast-growing 76’during the active phase by the method of differential box-counting fractal dimension. The fractal characteristics of differentiated xylem cells as well as the relationship between fractal dimension and tissues proportion were considered. Results showed that the fractal dimensions of cross sections were larger than those of tangential sections. Fractal dimension of cross sections had a remarkable negative correlation with the ratio of vessel element, significant positive correlations with the proportion of wood fiber and the proportion of parenchyma. The correlation of fractal dimension with wood fiber proportion was more significant than that with parenchyma proportion. The results were also verified by replacement of the tissues in the cross section. It was observed that fractal characteristics of the wood microstructure were very much related to the proportions of different tissues of the xylem cells.