Abstract: This paper investigated the effects of bamboo vinegar on inhibiting germination of conidiophore in the lab, and controlling downy mildew of cucumber in the field with ‘JinYou 30’ cucumber (Cucumis sativus L.). It showed that 100 times diluted bamboo vinegar could efficiently inhibit germinating on sporangium of downy mildew of cucumber, and could control the harm on cucumber in the field. The effects of repression to microorganism and prevention plant diseases could equate with 600 times diluted 72%Curzate.