The invention discloses a using method of an anti-disease composition of corn ear conidia. The using method comprises the following steps: A, preparing an original liquid which comprises 12% triadimefon wettable powder, 10% polyethylene glycol, monopotassium phosphate, artemisinin, indirubin, carboxymethyl cellulose sodium, oxalic acid and 5% aluminum sulfate; B, cultivating corn: selecting disease-free corn seeds, soaking the corn seeds by the original liquid in a 400 times in volume ratio for 1.5-2 hours, and taking out the corn seeds, washing the corn seeds by clean water, and drying the corn seeds in the sun, accelerating germination and seeding; C, during disease, adding water into the original liquid to be diluted to 600 time liquid for spraying work; and C, while spraying, adding water into the original liquid to be diluted to 500 time liquid for root irrigating operation. The using method disclosed by the invention is simple, and the used product is simple in using method, simple in proportion, convenient to use and good in northern leaf spot treatment effect. Tests show that 400-600 time liquid of the mixture has an obvious inactivating effect on conidiophore and conidia of pathogenic bacteria, and is good in sterilizing effect.