The invention relates to a preparation method of an amino polyether organic silicon compounded antifoaming agent. The method comprises the following technological steps: (1) adding allyl glycidyl ether and a platinum catalyst into a container, heating under stirring and reflux condensing conditions in the protection of N2, adding a toluene solution of hydrogen-containing silicone oil when the temperature rises to a certain level, after the reactions, removing the solvent and substances with low boiling points in a rotary evaporator, and drying so as to obtain epoxy modified silicone oil; (2) adding the epoxy modified silicon oil obtained in the step (1) and an ethanol solution of polyether amine into a container, heating under stirring, carrying out reactions under the reflux condensing conditions in the protection of N2, after the reactions, removing ethanol in a rotary evaporator, and drying so as to obtain amino polyether organic silicon; (3) compounding the amino polyether organic silicon obtained in the step (2) with a certain amount of silicone cream, a mixed emulsifier, and a thickening agent to prepare the amino polyether organic silicon compounded antifoaming agent. In the provided method, amino polyether organic silicon is prepared through a silicon-hydrogen addition / amination reaction and then is compounded with an emulsifier, a thickening agent, and silicon cream so as to prepare the amino polyether organic silicon compounded antifoaming agent, which can be dissolved in water quickly, has the advantages of excellent heat resistance, acid resistance, alkali resistance, and antifoaming property, and has the same performance as that of antifoaming agents in the market.