Provided is a wide-range diaphragm gas meter, comprising a machine core. The machine core comprises a diaphragm chamber, two diaphragms, two diaphragm covers, a valve cover, and a four-axis rotational system. The diaphragm chamber comprises a valve seat and two measuring chambers, and the two diaphragms are located in the two measuring chambers respectively. Each of the diaphragms is connected correspondingly to the four-axis rotational system. A vertical shaft is fixedly connected to one end of a rotating bar, the other end of the rotating bar is hinged to one end of a connecting bar, and the other end of the connecting bar is hinged to a crank. The central shaft of the crank is a third rotating shaft. A central crankwheel is arranged on a central shaft. The valve cover and the central crankwheel are coaxially arranged.