The invention discloses a steel slag hot disintegrating device. A slag disintegrating pool is of a reversed cone, a lining board, an inner wall and an outer wall are arranged on the pool wall of the slag disintegrating pool from the inside to the outside in sequence, wherein a pore passage inclined upwards is arranged on the lining board, the lining board is fixedly connected with the inner wall,a gap is left between the lining board and the inner wall, the inner wall and the outer wall form a hollow cavity, a supporting frame is arranged at the outer side of the outer wall, and a water inlet and a water outlet are respectively arranged at the upper end and the lower end of the outer wall; a slag tapping device is arranged at the lower end of the slag disintegrating pool, and a slag poking device, a slag guide plate and a steel slag delivery device are arranged below the slag tapping device; and a water seal device is arranged at the upper end of the slag disintegrating pool, a waterjacket type pool cover is put on the water seal device, a water inlet pipe, a spraying nozzle, a safety valve, a heating pipe, a water filling opening, a thermometer and a pressure gauge are arrangedon the pool cover, one end of the heating pipe is arranged in the water jacket, the other end of the heating pipe extends into the slag disintegrating pool, the spraying nozzle is installed at the tail end of the water inlet pipe and the water filling opening is communicated with the water jacket. The invention has the automatic slag tapping function and the waste heat recovery function, the steam at the upper part of the slag disintegrating pool reflows and infiltrates to the inside of the slag disintegrating pool through the pore passage on the lining board, and the hot disintegrating effect is further improved.