The defoamer in this invention mainly comprises the following components: higher fatty alcohol, higher fatty alcohol polyether, polyether containing nitrogen, fatty acid ester, the mixture of dewatering particle and mineral oil, emulsifier and water. The preparing process is as follows: premixing the defoaming active substance with the emulsifier, heating the systematic temperature to a certain temperature, adding water slowly into it, determining whether passing the colloid grinder in accordance with the emulsion diameter, generally, the emulsion diameter is smaller than 15 um. The defoamer in this invention mainly solves the problem of the weakening of the property of the high temperature emulsifying and defoamer with the elevation of temperature, the product is safe and high effective, and suit for the paper making coating and paper bladder defoaming.