Abstract: Taking ‘Chardonnay’ grape leaves as materials, in vitro leaf inoculation method and field spray method were used to explore the control effect of four kinds of compound Bacillus agents on grape downy mildew, in order to provide scientific reference and technical support for biological control of grape downy mildew.The results showed that four kinds of compound Bacillus agents could effectively control grape downy mildew.In the laboratory prevention and treatment test, the efficacy of compound Bacillus agent Ⅳ was the best when diluted 50 times, 82.51% and 83.16%,respectively.Compared with other agents, the EC₅₀ value of the compound Bacillus agent Ⅳ was the smallest and the bacteriostatic activity was the highest, which were 5.00×10~7 cfu·mL^-1 and 3.95×10~7 cfu·mL^-1,respectively.In the field control test, compound Bacillus agent Ⅳ had better control effect on downy mildew of grape with long duration and stable efficacy.The control effect of compound Bacillus agent Ⅳ after 4 times of continuous application could reach 80.39%,It coud be used as the raw and preventive medicine to prevent grape downy mildew in production.