The invention provides a synergist for refractory copper oxide ore flotation and a preparation method thereof, and belongs to the technical field of flotation. The synergist comprises, by weight, 60 parts of 8-hydroxyquinoline, 45 parts of dioctyl phosphate, 15 parts of ammonium sulfate, 5 parts of kerosene and 5 parts of ethanol. The preparation method comprises the steps of firstly mixing the powdery 8-hydroxyquinoline and ammonium sulfate, then mixing the liquid dioctyl phosphate, kerosene and ethanol, adding the powdery solids into the mixed liquid medicament solution, next adding water soas to prepare the water solution with the volume fraction of 30%-35%, heating to 40-50 DEG C in a microwave field, and stirring for 15-20 min. The prepared synergist can be directly added into the ore grinding operation in the form of a stock solution. The synergist for the refractory copper oxide ore flotation is stable in property, good in solubility, high in activity, less in dosage of the medicament, high in adaptability to ores and capable of effectively improving indexes of the refractory copper oxide ore flotation, and has obvious technical and economic indexes and environmental benefits.