The invention discloses a polycrystalline silicon ingot casting molten material and an impurity removing process. The process comprises the following steps: 1, preheating: adopting an ingot furnace to preheat a silicon material filled in a crucible, and gradually raising the heating temperature of the ingot furnace to T1; the preheating time is 6-10h, and T1=1165-1185 DEG C; 2, melting: the melting temperature is T1-T5; T5=1540-1560 DEG C; in the melting process, filling insert gases into the ingot furnace, and keeping air pressure in the furnace in Q1, and Q1=550-650mbar; 3, removing impurities: the process is as follows: the 11th step, reducing pressure: the air pressure of the ingot furnace is reduced from Q1 to Q2, and the pressure reducing time is 8-12min, and Q2=350-450mbar; the 12th step, maintaining pressure; the 13th step, boosting pressure and lowering temperature. The process has the advantages of simple steps, reasonable design, convenience in realization, easiness in grasp and good using effect, can discharge gas containing carbon in the furnace in time, and increases the polycrystalline silicon ingot casting quality.