Fecha de publicación: 25/12/2020 Fuente: WIPO "tobacco agriculture" The invention relates to the technical field of tobacco agricultural microbial fermentation, and particularly relates to a preparation method of a composite biocontrol microbial inoculum for preventing and treating tobacco black shank. The strain of the composite biocontrol microbial inoculum comprises paenibacillus polymyxa -LB-9 and trichoderma aureoviride -YCS-Tr2. The method comprises the steps of culturing a paenibacillus polymyxa -LB-9 strain by using an LB culture medium, and culturing a trichoderma aureoviride -YCS-Tr2 strain by using a potato dextrose agar culture medium, thereby respectively preparing paenibacillus polymyxa -LB-9 fermentation liquor and trichoderma aureoviride -YCS-Tr2 fermentation liquor; mixing the prepared paenibacillus polymyxa -LB-9 fermentation liquor and the prepared trichoderma aureoviride -YCS-Tr2 fermentation liquor according to the volume ratio ranging from 1: 1 to 1: 2, and concentrating the prepared mixed liquor by 10 times so as to prepare biocontrol bacterium fermentation liquor; and preparing an auxiliary agent formula which comprises the following raw materials: naphthalene sulfonate, magnesium aluminum silicate, xanthan gum, glycerol andKathon, and mixing the prepared biocontrol bacterium fermentation liquor with the auxiliary agent formula, thereby preparing the composite biocontrol microbial inoculum.