The invention discloses a method for preparing an anti-type A botulinum neurotoxin immunoglobulin antibody, which comprises the steps of preparing and obtaining the anti-type A botulinum neurotoxin immunoglobulin antibody through taking type A botulinum neurotoxin recombinant protein rAHc as immunogen to immunize animals. The method for preparing the anti-type A botulinum neurotoxin immunoglobulin antibody eliminates a Fc segment in the antibody which can cause side effect and obtains the horse anti-type A botulinum neurotoxin immunoglobulin F(ab')2 antibody; after blood serum obtained by pentalogy hyper-immune and hexalogy hyper-immune are mixed, the content (purity) of F(ab')2 of the antibody can achieve 80.2 percent in a semi-finished product obtained through further purification; the titer of the antibody can achieve 8000 IU/ml; the antibody has good specificity and sensitivity to type A botulinum neurotoxin; and the purity and the specific activity of the antibody are higher than the antitoxin prepared from the traditional toxin immunity horses. Moreover, the invention has the good stability and safety.