The invention discloses processing method and device of high-temperature solid steel slag. In the processing method, the front of the traditional working cylinder is provided with a feed cylinder capable of containing a sufficient quantity of the high-temperature solid steel slag; the side surface or the end surface of the feed cylinder is provided with an automatic opening and closing door; the feed cylinder and the working cylinder are on a same axial line and rigidly fixedly combined together to form a large cavity, and the axial line forms a certain tilt angle outwards with a horizontal plane; the high-temperature solid steel slag is poured into the feed cylinder for one time during feed; a sealing door is automatically closed and locked after the feed is completed, the feed cylinder rotates according to set direction and speed under the action of a transmission device, and the high-temperature solid steel slag inside the feed cylinder gradually moves downwards with the rotation of the feed cylinder and feeds spirally to sequentially enter the working cylinder; the high-temperature solid steel slag inside the feed cylinder is continuously cooled and smashed with the rotation of the working cylinder, and finished product slag reaching certain granularity is delivered out of the working cylinder through an output device. The invention can realize the cleaning and efficient processing of the high-temperature solid steel slag.