The invention discloses a polycrystalline silicon cast ingot growth control method and a process. A temperature difference between the top and the bottom of a crucible is adopted as a newly introducedparameter delta t for controlling growth with a polycrystalline silicon cast ingot growth process; in the preparation process of cast ingots, a curve delta t is firstly increased and then reduced, and is further increased and finally reduced to 0; when the value delta t reaches the maximum peak, a silicon material inside the crucible starts to be molten, the value delta t has a peak of minimal values when the silicon material is completely molten, the temperature of the peak of the value delta t cannot be lower than 160 DEG C, once the temperature is lower than 160 DEG C, a melt-through phenomenon can be caused for a seed crystal layer at the bottom of the crucible, a red zone can be increased, and at the same time the red zone at a corner of the crucible can extend upwards along the wallof the crucible. A delta t peak judging method can be used as a criterion of the silicon ingot casting process, the polycrystalline silicon cast ingot growth process is provided, and the polycrystalline silicon cast ingot growth control method has the advantages that the thickness of a red zone in polycrystalline silicon is reduced, the quality of the polycrystalline silicon is improved, the utilization efficiency of the polycrystalline silicon is improved, and the cost is lowered.