The invention relates to a piling mechanism for a metal powder machining boss. The piling mechanism comprises a supporting platform and an upper support. Piling die pushing cylinders are arranged on the front side, the rear side, the left side and the right side of a main plate and connected with piling die pushing blocks. The four piling die pushing blocks can form an opened square die with sidefaces closed. A feeding device is arranged over the square die, and comprises a feeding lifting cylinder arranged below the upper support. The lower portion of the feeding lifting cylinder is connected with a feeding lifting block. The lower portion of the feeding lifting block is connected with a feeding cylinder. The upper portion of the feeding cylinder is communicated with a discharging box. The lower end of the feeding cylinder is provided with a sealing cover plate. A discharge port is formed in the lateral side of the bottom of the feeding cylinder. Pressing lifting cylinders are arranged at the upper portions of the piling die pushing blocks and connected with pressing lifting bases. The pressing lifting bases are connected with pressing blocks. The four pressing blocks form a square pressing plate with a hole in the center. The size of the square pressing plate is matched with a square die. The boss forming efficiency is improved, and meanwhile cost is reduced.