The invention discloses a packing box sealing structure of a high-temperature ball valve. A packing box is arranged at the upper end of a valve body; packing is arranged between the packing box and a main shaft; a packing box gland is formed at upper ends of the packing and the packing box; the packing comprises a plurality of layers which are arranged from the lower part to the upper parts as follows: the first layer and the last layer adopt flexible graphite packing; three to five layers of flexible graphite rings are formed in the middle; a layer of gland sealing ring is also provided; the gland sealing ring adopts a metal ring; the gland sealing ring is positioned among the flexible graphite rings; a steam blowing pipe is connected with the outer part of the gland sealing ring. The packing box sealing structure not only improves the whole structure of a sealing piece group (packing), but also adds steam blowing, and greatly improves the overall life of the packing box sealing structure and the stability of a sealing pair.