The utility model discloses a mounting structure of clamping jaws of a tube expanding machine. The mounting structure of the clamping jaws of the tube expanding machine comprises a set of clamping jaws and a clamping jaw fixing plate. The fixed end of every clamping jaw is matched with the clamping jaw fixing plate is provided with a ring-shaped groove and a limiting strip which penetrates the ring-shaped groove and in clearance fit with the ring-shaped groove. The clamping jaw fixing plate is provided with a mounting hole adapted to the limiting strip. One end of the limiting strip extends out of the clamping jaw fixing plate. The mounting hole is in the structure of a U-shaped groove and arranged at the upper end surface of the clamping jaw fixing plate. The clamping jaw fixing plate is also connected to a pressure plate. The mounting structure of the clamping jaws of the tube expanding machine is simple in structure, easy to disassemble and assemble and capable of achieving rapid replacement of the clamping jaws and improving production efficiency and can be widely used in the field of tube expanding machines.