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 of P388 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 yunnanxane (3) was elucidated as taxa-4 (20), 11-diene-2 alpha, 5 alpha, 10 beta, 14 beta-tetraoln2 alpha,5 alpha,10 beta-triacetaten-14 beta-alpha-methyl-beta- hydroxylbutyratebyhighfield 1H NMR, 13C NMR, 1H-1HCOSY, 13C-1HCOSY, 13C-1HCOLOC and X-ray analysis. It showed the inhibitory effect on A2780 DDP, KB and HCT-8 cell line in vitro. All of the eight compounds were isolated from this species for the first time.