A new and 25 known taxane diterpenoids were isolated from the dried whole plants of Taxus wallichiana var. mairei cultivated in the southern area of the Yangtze River in China. The chemical structure of new compound 1, named taxiwallinine, was established by means of MS and NMR analyses. Among the 25 known taxane compounds 2-26, compounds 10, 12, 14, 15, 17 and 21-23 were first isolated from this plant. Taxiwallinine and taxol were screened for the cytotoxic effect on human breast cancer cell line MCF-7 with IC50 values of 20.898 μg/mL and 0.008 μg/mL, respectively. Taxiwallinine showed moderate cytotoxicity to this cell line. These results demonstrate that T. wallichiana var. mairei cultivated in the southern area of the Yangtze River in China could be a renewable resource for extracting the taxane derivatives and the new compound, taxiwallinine, could be a potential anti-tumour product.