Mine-used tri-ring chains have been bent by hand in some machine-mining enterprises. However, this type of process is old-fashioned. The labor intensity of operating workers is high and production efficiency is low. At the same time, the production quality is also unstable. This type of process has not adapted itself to the manufacture of the product. So, for the mine-used tri-ring chains, a novel and simple auto-bending ring machine has been designed. The machine has the advantage of a simple frame, convenient mould-removal, production efficiency, steady production quality, and so on. The machine can be used for medium and small manufacturing. The machine can also be adapted for auto-bending of tri-ring chains if it is equipped with a delivery device, heating device and the appropriate controlling circuit.