The cooler is also known as the rotary drum cooler. In the compound fertilizer production, it can cool the fertilizer with certain temperature and grain size and be used with the dryer. It can greatly improve the cooling rate, reduce the labor intensity and increase the yield, further remove some moisture and reduce the particle temperature of the compound fertilizer. At the same time, the cooling machine also can be used for the cooling of other powdery and granular materials. The cooling machine has simple structure, good stability and reliable operation.