The invention provides a method for preparing an anti-acetochlor soybean rhizobium inoculum, and belongs to a microbial inoculum preparation technology; the method uses soybean rhizobia with highly efficient nitrogen fixation activity to increase the concentration of acetochlor gradually in a sucrose yeast extract culture medium, and to culture resistant soybean rhizobia under the condition of acetochlor high-pressure selection to form a spawn of the anti-acetochlor soybean rhizobia after pure lien separation, and then selects the spawn into a sloped tube to form a primary strain, propagates the primary strain to form a secondary strain and inoculates the secondary strain to a fermentation tank to produce the microbial inoculum; the method has a simple process, low production cost, and the preparations prepared by the method has high performance and quality and can avoid damages to nitrogen fixation of soybean rhizobia by acetochlor during use and improve the yield and quality of soybean.