The invention relates to a preparation method for a bacillus coagulans bacterial suspension. The preparation method comprises the following steps: inoculating a bacillus coagulans CGMCC No.6681 strain into a flat plate of a solid culture medium for activating bacteria, then carrying out seed culture and fermentation culture, finally, centrifuging the fermentation liquor obtained by the fermentation culture, removing supernatant, taking bacterial sludge, blending with sterile water to prepare a 5*10<10> to 8*10<10>cfu/mL bacterial suspension, and then adding a surfactant to obtain the bacillus coagulans bacterial suspension. The bacterial suspension prepared by the method disclosed by the invention is enhanced in plant body surface colonization capacity, and integrates growth promotion, bacterium inhibition and insect killing; the multiple effects of the bacterial suspension determine that the bacterial suspension has great prospect in popularization and meets the requirements of modern agriculture.