Abstract: In order to determine the field control effect and optimal dosage of 28% ametoctradin and fluopicolide suspension on potato late blight, the field efficacy test was conducted by means of stalk and leaf spray treatment and regular investigation. The results showed that: Under the dosage of 210.0-315.0 g·ha^-1, the control effect of 28% ametoctradin and fluopicolide suspension on potato late blight could reach 79.66%-87.56% after 10 days of the first application. 10 days after the second application, the control effect of potato late plague was from 80.68% to 88.60%, which was significantly better than that of the control agent, and the dosage of corresponding effective components was less than that of the control agent. After two rounds of application, the damage level to potato was 1.0 for 5 days, and no significant damage to potatoes was observed. Compared with the control group, the yield increase rate was 16.34%-24.28%. Considering the cost and effect of medication, the recommended dosage of active ingredients was 210.0-315.0 g·ha^-1. The suspension of 28% ametoctradin and fluopicolide can effectively control potato late blight and has good safety for potato.