The invention discloses a Nimesulide injection for livestock and a preparation method thereof. Each 100mL of injection comprises the following components: 2-10g of Nimesulide, 2-10mL of ethanolamine, 0.2-0.4g of sodium sulfite, 0.01-0.02g of disodium ethylene diamine tetraacetate and balance of water for injection, wherein the pH value is regulated to 7-9 with lactic acid. The preparation method of the Nimesulide injection for livestock mainly comprises the steps of liquid preparing, filtering, sterilizing and the like. The injection can be used through intramuscular, subcutaneous or intravenous administration, has obvious effect, no first pass effect of the liver, high bioavailability, simple preparation processes, stable, safe and effective products and low cost, is suitable for industrial mass production, and has wide market prospects.