The utility model belongs to the technical field of polysilicon casting equipment, particularly to a graphite solidification aid used for polysilicon directional solidification, which comprises a base, a groove formed at the lower part of the base, and a cooling pipe embedded into the base through the groove. The cooling pipe is filled with cooling gas or cooling liquid, so as to achieve the purpose of reducing the transverse temperature gradient and obtain a flat interface. Besides, by adjusting the distribution density and the distribution depth of the solidification aid in the cooling pipe and the size of the cooling pipe, the cooling position and the cooling area are controlled and the cooling capacity is controlled as well, thereby controlling the nucleation point at the early stage of crystal growth to produce large-size crystal grains. Therefore, the quality of the polysilicon ingot is improved.