The present invention discloses a die-casting die for die-casting formation of thin-walled workpieces. Surface structures and sizes of matching surfaces of a finished thin-walled workpiece are formed and defined by the die-casting die, and flat ejector pins in the die-casting die are arranged in positions corresponding to an exhaust end of the thin-walled workpiece in the die-casting die. A thin-walled workpiece forming process is also disclosed. In the process, the above die-casting die is used for die-casting formation of the thin-walled workpieces. By controlling the size of the die, the surface structures and the sizes of the matching surfaces of the die-cast thin-walled workpiece right accord with the surface structure and the size of the finished product. By this means, machining allowances set on the matching surfaces, and arrangement of computer numerical control (CNC) machining assisting stages and ejector pins on the stages during die-casting formation of the thin-walled workpieces are thus omitted, and an additional CNC machining process of the matching surfaces after die casting of the thin-walled workpieces is also omitted. By this means, the aims of avoiding deformations of the thin-walled workpieces in the CNC machining process and ejection deformation of the thin-walled workpieces in the die-casting process are achieved.