This experiment was carried out to explore the effects of microbial pesticides on control of cucumber downy mildew. Three kinds of microbial pesticides (Recharge, Dynamic F, and 3.0% amino-oligosaccharin AS) were used and clean water was taken as the control (CK). The experiment showed that Recharge and 3.0% amino-oligosaccharin AS had better control effect on cucumber downy mildew. After the first application, the average control effect of Recharge and 3.0% amino-oligosaccharin AS was higher than 50%. After the third application, the average control effect of Recharge and 3.0% amino-oligosaccharin AS was higher than 20%. The control effect of Dynamic F on cucumber downy mildew was relatively poor, and the average control effect after the first application was 38.34%, and the average control effect after the third application was only 15.64%. According to the experimental results, the average control effect of three pesticides after application showed a gradual decline trend.