A gear-rack type mechanical lower material jacking device for a mechanical press machine comprises a sliding block mounted on a machine body. Upper pull rods are vertically arranged on the two sides of the sliding block correspondingly and connected with lower pull rods through adjusting nuts, the lower ends of the lower pulling rods are connected with vertically-arranged racks, and the racks can vertically move along rack seats arranged at the bottom of the machine body and are in matched connection with gears; the two gears are mounted on a transversely-arranged shaft, the shaft is mounted on a shaft supporting seat arranged at the bottom of the machine body, a cam is arranged in the middle of the shaft, and a lower jacking rod connected with the cam in a matched mode is vertically arranged above the cam; the upper end of the lower jacking rod penetrates through the machine body and is in sleeving connection with an upper jacking rod, the lower end of the upper jacking rod penetrates through a transversely-arranged material jacking lever and is sleeved with the lower jacking rod, and the upper end of the upper jacking rod is connected with a work table in a matched mode; and one end of the material jacking lever is rotatably connected with the machine body, and the other end of the material jacking lever is connected with an air cylinder. The gear-rack type mechanical lower material jacking device for the mechanical press machine has the advantages of being good in forging and extruding or stretching synchronicity, compact in structure, balanced in symmetry, safe, reliable, high in mechanical efficiency, low in manufacturing cost, high in product quality and the like.