Fuente: WIPO "tobacco agriculture" The invention provides alternaria alternata inoculation liquid and a preparation method thereof. The preparation method comprises the following steps: culturing alternaria alternata on a PDA (potato dextrose agar) plate at 28 DEG C for 6-7 hours, and preparing 1*10cfu/ml of spore suspension liquid, namely the alternaria alternata inoculation liquid, from 0.5%-1.5% (v/v) of glucose liquid and 0.5%-1.5% (v/v) of tween-20. According to the alternaria alternata inoculation liquid, the incidence rate of tobacco plants can be effectively increased through direct field spraying inoculation; in addition, the preparation method is simple, practical, and easy to operate and popularize.6>