Abstract: Field control efficacy of azoxystrobin(Amistar) on cucumber downy mildew, pepper brown leaf spot, tomato early blight as well as its toxicity to their pathogenic fungi was investigated. The EC50 to Pseudoperonospora Cubensis, Collecterichum capsica, Aternaria solani are 0.004 9 μg/mL, 5.6345 0 μg/mL, 8.6176 μg/mL, respectively. Field experiments showed this fungicide was very efficacious on controlling those diseases, and their efficacies are over 80 percent. At the same time, this fungcide was also very safe to vegetables. When sprayed at 500 μg/mL, a concentration more than two times higher than used in the field, which did not induce any harmful effect on vegetable development and growth.The study indicated that azoxystrobin be used three times successive could control those diseases,and was safety to plants.