The invention discloses a metal gravity casting automatic production line, which arranges a circular rounding track on ground, and a plurality of gravity casting machines are placed on the track. The bottom of the casting machine is provided with wheels contacting with the track, the center of the rounding track is provided with a turning device used for driving the casting machines to carry out synchronous movement, the turning device is connected with the casting machines by connecting arms respectively, the casting machines are evenly distributed around the turning device, the turning device is connected with a driving motor by a reducer, the circumference of the circular rounding track is externally provided with a smelting furnace, a manipulator used for conveying metal solution is arranged beside the smelting furnace, and the casting machine, the motor and the manipulator are connected with a control center by electrical signals. The metal gravity casting machine completes casting processing in the circulating motion process, thus not only reducing the occupied premises, the staff and the labor intensity, but also eliminating unsafe factors, greatly increasing the productionefficiency, and reducing the production cost.