The invention discloses an overflowing isolation device for a polysilicon ingot furnace and solves the problem of safe and effective isolation of a high-temperature overflowing liquid silicon material in the polysilicon ingot furnace from the bottom of the ingot furnace. The bottom of a lower furnace body of the polysilicon ingot furnace is provided with a thermocouple installation bucket-shaped seat (9), the top end of the thermocouple installation bucket-shaped seat (9) is arranged in the lower furnace body of the polysilicon ingot furnace and sleeved with a stainless steel cylindrical barrel (4), the stainless steel cylindrical barrel (4) is sleeved with an inverted umbrella-shaped overflowing cotton supporting frame body (3), the circular umbrella body of the inverted umbrella-shaped overflowing cotton supporting frame body (3) is provided with an annular groove, a first layer of annular overflowing cotton cushion (8) is inserted into the annular groove, and the first layer of annular overflowing cotton cushion (8) is fully laid on the inner side face of the inner wall (2) of the lower furnace body of the polysilicon ingot furnace. The overflowing isolation device guarantees safety of the production process of the polysilicon ingot.