The invention relates to a cold-rolling flying shear synchronous connection shaft device and a manufacture method, and the device is fixed between frames on two sides of a cold-rolling flying shear. The device is characterized by comprising three sections of shafts which are connected in linear mode, and a second section of shaft is located in the middle of a first section of shaft and a second section of shaft and is connected with the shafts at two ends of the second section of shaft through flanges. By means of a synchronous connection method, the cold-rolling flying shear synchronous connection shaft device and the manufacture method change a single long shaft connection method into a mutual connection method among three sections of independent shafts, well solve the problem of maintenance difficulties caused by the single long shaft connection method under the condition of ensuring coaxiality and shearing strength and precision, and has good practical operability.