Abstract: With dividing the branches & stems diameter (Φ) of 4.5-year old Taxus yunnanensis sample trees into 9 grades, the biomass characteristics of bark and xylem in different grades were analyzed, and taxanes contents of different diameter samples, such as 10-DAB, baccatin-Ⅲ, 7-xyl-taxol, 10-deacet-taxol, cephalomannine, and taxol, were tested and contrasted. The results indicated that there was a significant decline for the proportion of samples′ bark when Φ > 0.5 cm, and when Φ > 0.8 cm, there was the significant increase for the diameter of samples′ xylem. When 0.3 cm < Φ < 1.49 cm and Φ > 4.00 cm, the ratio of dry weights of samples′ bark and xylem decreased significantly with the increase of the diameter. There was a certain amount of taxol and other taxanes in the stem xylem of the saplings. And Φ=0.3 cm, the branch diameter of the tree species, which was the significant node that relates to changes of taxanes contents of the branches. We thus suggest that the small branches with leaves (Φ < 0.3 cm) be used as main target and pricing basis in the cultivation, harvesting, and the purchase of the branches and leaves of medicinal raw material forests of T.yunnanensis.