The invention relates to a polycrystalline silicon ingot casting device, belongs to the field of a photovoltaic technology, and solves the problem that in the prior art, the polycrystalline silicon ingot has high dislocation density. The polycrystalline silicon ingot casting device comprises a furnace body; a heat-insulating cage capable of doing lifting motion is arranged in the furnace body; a crucible, a crucible protective plate, a graphite bottom plate, a graphite cover plate, a top hater and a side heater are arranged in the heat-insulating cage; the graphite bottom plate is placed on aheat exchange platform; the crucible is placed on the graphite bottom plate; an auxiliary cooling device is arranged on the heat exchange platform; the auxiliary cooling device can adjust the coolingtemperature. The polycrystalline silicon ingot casting device is provided with the auxiliary cooling device and the heat exchange efficiency of the heat exchange platform at the bottom can be adjusted, so that the temperature gradient of the bottom and the side of the silicon ingot is uniform, the transverse temperature difference of a solid and liquid interface is eliminated, the long crystal direction is stable and the dislocation density is reduced.