The utility model discloses an automatic tensioning machine, including the stretching -drawing machine body, the stretching -drawing machine body includes frame, pneumatic cylinder and steel wire clip head, steel wire clip head and frame sliding connection, and the piston rod of pneumatic cylinder can be dismantled with the left side of steel wire clip head and be connected, and the right side of steel wire clip head is connected with the pier nose that is used for suppress the end of steel wire or reinforcing bar, the mound is thick, still include hold -down mechanism, hold -down mechanism includes last holder that cylinder and lower surface and upper surface can laminate and holder down, and lower holder is fixed in the frame, is equipped with the ascending guide bar of vertical side on the lower holder, goes up the guiding hole that is equipped with on the holder with guide bar sliding fit, goes up the holder and passes through guiding hole and guide bar sliding fit, the lower surface of last holder and the upper surface of lower holder all are equipped with relative up -down's half slot. This stretching -drawing machine is the improvement of going on current steel wire straining means, and to carrying out the processing that the mound is thick to the end of steel wire or reinforcing bar before the steel wire stretch -draw, it is also very convenient to use.