The invention discloses an efficient spraying method of an isolation agent, and relates to the technical field of steel rolling. The efficient spraying method comprises the following steps that S1, ablank is selected, the thickness of a lower blank is increased by a certain value on the basis of target thickness in the cogging process, and the increased thickness is used for machining and grooving; S2, a blank plate of the initial size is milled, and the milling depth and speed are controlled in the milling process; S3, a square shoulder milling cutter is selected for machining and grooving the surface of the lower blank, and the edge welded to an upper blank is reserved around the blank; and S4, a corn milling cutter is used for machining the inner corner of a groove. The method is a solution scheme provided for the situation that in the assembly process of symmetric rolling or ply rolling composite plates, the isolation agent is prone to being damaged, and difficulty is brought to quality and production; and the groove is formed in the surface of the lower blank, the isolation agent is sprayed in the groove, the isolation agent is prevented from being in contact with the surfaceof the blank, and then the isolation agent is prevented from being damaged in the assembly process.