The utility model provides a heavy tractor, which comprises a driving chamber assembly and a bottom plate assembly, wherein, the bottom plate assembly mainly comprises an engine, a gear-box, a stander, a front bridge, a duplex transfixion driving bridge, a driving bridge, a battery cell box, a fuel tank, a wheel, a steel plate spring suspension fork, an air ballonet switch device, a gear axis and a braking device. The stander is provided with the engine that is connected with the gear-box. The side face of the stander is provided with the battery cell box and the fuel tank. The front bridge is connected with the stander by the steel plate spring suspension fork. The duplex transfixion driving bridge and the driving bridge are arranged below the stander by the air ballonet. The gear-box is connected with one end of the gear axis, while the other end of the gear axis is connected with the duplex transfixion driving bridge. The duplex transfixion driving bridge is connected with the driving bridge. The utility model overcomes the drawbacks of the prior tractor and has the advantages of large loading capability, high speed, low center of gravity and safe running performance.