Hyphae and conidia of Botrytis cinerea treated with wuyiencin were observed under the light microscopy (LM) and transmission electron microscopy (TEM). Compared with the control of whose hyphae were generally uniform in shape, wuyiencin treatment caused abnormal growth of hyphae and enlarged and constricted forms of conidia tube. Cellular leakage was observed when wuyiencin was used in high concentration. Radio labeled ¹⁴C-glutamate, ³H-glucosamine and ³H-adenine incorporation experiments showed that wuyiencin strongly inhibited protein synthesis, but had no effect on cell wall and nuclear acid synthesis of B. cinerea. Our results suggest that the inhibition of protein synthesis is the primary action of wuyiencin.