The invention provides a scopolamine butylbromide injection and a preparation method thereof. The scopolamine butylbromide injection comprises 200 mg of scopolamine butyl bromide, a pH buffer of 10-100 mg, a stabilizer of 1.2-36 mg, water for injection to 10 ml, and the injection The pH value is 4.8-5.4, and the following method is used for preparation: (1) Take 60-80% of the formula amount of water for injection, add the prescribed amount of pH buffer pair, stir for 10-30min to completely dissolve it, and control the pH to 4.8-5.2 (2) Add the prescribed amount of scopolamine butylbromide, stir and dissolve; add the prescribed amount of stabilizer and remaining water for injection, and stir for 15-45min; (3) Filter through a 0.22 μm microporous membrane, fill, and prepare and fill Fill it with nitrogen protection during the loading process, and sterilize it at 121°C for 12 minutes. The scopolamine butylbromide injection of the invention can effectively promote smooth muscle spasmolysis of patients, has little adverse reaction, high storage stability, simple process and low production cost.