This paper studies the synthesis process of aspirin calcium. First, aspirin, anhydrous calcium nitrate, ethanamine, synthesized calcium aspirin, post-aspirin calcium chelate with urea to produce calcium aspirin. This topic replaces ethanolamine instead traditional ammonia or ammonia gas, environment friendly and easy to control. With ethanol as the solvent, the effects of reaction temperature, reaction time and reaction pH of calcium aspirin and urea were studied. The experimental results show that the reaction temperature is 30 ~ 35 ℃, reaction time of 2 h, reaction pH is 7.5, yield of aspirin calcium is 96.6%, purity is 98.7%, meeting the veterinary drug quality standard.