The invention provides a method for synthesizing a fluorine silicon antifoaming agent for engine oil. According to the method, organosilicone monomer hexamethyl cyclotrisiloxane or octamethylcyclotetrasiloxane serves as the main raw material, under the action of a catalyst, an end-capping reagent is added, a reaction with 1, 3, 5-tris (3, 3, 3-trifluoropropyl) methylcyclotrisiloxane is conducted, after the reaction is completed, low molecular substances are removed, and after filtering is conducted, the fluorine silicon antifoaming agent for engine oil is obtained. The fluorine silicon antifoaming agent has the advantages of being good in solubleness and good in high-temperature anti-foaming property and is low in production cost and free of pollution; the fluorine silicon antifoaming agent is mainly used for engine oil of the APISJ level, the ILSAC CF-4 level and above, the problem of high-temperature (150 DEG C) foaming resistance of oil is solved, and the engine oil is good in foam characteristic and ideal in high-low-temperature resistance performance.