Abstract: The ethanolic extract of the bark of Taxus yunnanensis Cheng et L.K. Fu. showed significant antineoplastic effect on the transplantable tumors in mice. The life survival ofP388 leukemic bearing mice was increased (84%)and the growth of B₁₆ melanoma in mice was inhibited (53%). From this extract eight taxane diterpenoids and taxane alkaloids have been isolated.Seven of them have been identified as taxinine E(1), taxinine J(2), 1-acetoxy-5-deacetyl baccatin Ⅰ(4 ), baccatin Ⅲ(5), taxol (6), cephalomannine (7), 7 -xylosyl-10 -deacetyl taxol (8)from their physical and spectroscopic properties. A new taxane diterpenoid, named yunnanxanc (3) was elucidated as taxa-4 (20), 11-diene- 2α, 5α, 10β,14β- tetraoln2α,5α,10β- triacetaten-14β-α-methyl-β- hydroxylbutyratebyhighfield ¹H NMR, ¹³C NMR, ¹H-¹HCOSY, ¹³C-¹HCOSY, ¹³C-¹HCOLOC and X-ray analysis. It showed the inhibitory effect on A_(2780) DDP, KB and HCT-8 cell line in vitro. All of the eight compounds were isolated from this species for the first time.