Abstract: The toxicity determination of preparation whose effectual component was natamycin to Conielladiplodiella(Speg.) Petrak&Sydow、BotrytiscinereaPers、Sphacelome ampelinum Bary, were tested using hyphal growth rate and the EC50 were 29.67, 35.79, 32.08μg/ml respectively. The efficacy of controlling diseases were tested by pathogenic infection of the three fungal diseases. The mould inhibitor control efficacy of different time were 80.18%, 55.5%, 65.17% at the dosage of 200μg/ml respectively, and carbendazim control efficacy were 19.82%, 16.5%, 21.72% at the dosage of 1000μg/ml respectively. The conclusion was that the preparation had higher control efficacy than carbendazim, and the difference between preparation and carbendazim was significant.