The present invention relates to the field of manufacturing technologies of semiconductor power devices, and more particularly to a method for manufacturing a split-gate power device. In the method for manufacturing a split-gate power device according to the present invention, lateral etching is added to form lateral recesses of a control gate groove below a first insulating film in a process of forming the control gate groove by etching, and therefore, after a first conductive film is deposited, the first conductive film can be directly etched by using the first insulating film as a mask to form control gates. The technical process of the present invention is simplified, reliable and easy to control, and can greatly improve the yield of the split-gate power device. The present invention is particularly suitable for the manufacture of 25V-200V semiconductor power devices.