Forging die, piston forging method and piston

The invention discloses a forging die, a piston forging method and a piston, the forging die is used for processing a deep-cylinder thin-wall piston forge piece on a die forging hammer, the forging die comprises a punch, the punch is provided with an impact end and a fixed end, and the shape structure of the impact end is matched with the shape structure of the inner wall of the piston forge piece; the upper die block is provided with a fixing cavity matched with the fixing end, and the upper die block is provided with an axial positioning assembly used for axially positioning the punch; the lower module is provided with a cavity which is used for placing a blank and is opposite to the fixing cavity; and the limiting piece is used for limiting the stroke of the die forging hammer. The die is used for forging a piston, a heated forging blank is placed in the cavity and then is subjected to pressure bearing through the limiting piece to finish pre-forging, then the limiting piece is taken down to finish precisi