The invention discloses a compound gentamycin micronomicin sulfate injection and a preparation method thereof. Per 100mL of the injection consists of the following components: 0.8-2.2g of gentamycin micronomicin sulfate, 0.02-0.18g of cysteine hydrochloride, 0.01-0.20g of an antioxidant, 0.01-0.05g of a metal ion chelant, a pH regulator with a dosage sufficient to control the pH value of the system at 3.5-6.5, and the balance water for injection. According to the invention, gentamycin micronomicin sulfate and cysteine hydrochloride are combined into an injection drug, which has anti-inflammatory effect while reaching an antibacterial effect, can quickly relieve animal acute infectious diseases, shorten the healing period, and achieve the purposes of treating both symptoms and root causes. The compound gentamycin micronomicin sulfate injection has a reasonable prescription, is safe and stable, has treatment effect superior to that of gentamycin micronomicin sulfate single preparation, and the preparation process is simple, is convenient to operate, and is easy to realize industrialization. Compared with separate drug administration or multiple injection of antibacterial drugs and anti-inflammatory drugs, the compound injection provided by the invention also has the advantages of low cost, small dosage, convenient use, small animal stress response, and high treatment efficiency, etc.