The invention relates to a numerical control machining method for a thin-wall copper electrode, which comprises the following steps of: reasonably selecting a clamp, a cutter and a cutting parameter for improving the working efficiency; reasonably distributing the step and a feed route; controlling the deformation of a workpiece; after rough machining is finished, mounting a residual stress release notch at the side surface of the workpiece; eliminating deformation caused by residual stress during rapid rough machining, wherein a rough machining cutter adopts a ball end milling cutter instead of a generally used flat end vertical milling cutter; and carrying out symmetrical machining on the design of the feed route. The method for machining the workpiece sequentially comprises the steps of machining a reference surface 5 and a reference surface 4, clamping for positioning, roughly machining, machining a reference surface 2 and a reference surface 3, machining a stress release notch 9, finely machining and detecting precision. By adopting a plurality of process measures for controlling deformation, the invention has the advantages of greatly reducing the deformation of machining parts and effectively improving the precision and the stability of the parts. By actually measuring the workpiece on a three-coordinate measuring machine, a surface roughness value can be reduced to minimum and can completely meet the requirement on products.