A metal milling method comprises the following steps: firstly, according to preprocessing parameters, controlling the milling of a milling cutter on a workpiece, wherein the distance between the central shaft of the milling cutter and the workpiece is smaller than a specified tolerance range; secondly, controlling the milling cutter to move for at least one circle anticlockwise along the workpiece; thirdly, right now, with the full advantage of ploughing effect of side edges, processing the third surface and the fourth surface of the workpece by using the side edges of a first cutting tool and a second cutting tool, and measuring the tracks of the side edges according to calculation of a trigonometric function; fourthly, fixing the workpiece on the fourth working surface and the fifth working surface, milling by using the cutting tools through straight-line feeding along helical track; fifthly, after the processing of the workpiece is completed, demounting and cleaning, and chemically plating with milling waste liquid generated during milling at the same time so as to achieve the purposes of utilizing the waste and saving the energy. Because of the milling method provided by the invention, the existing milling equipment can be fully utilized.