The invention discloses a large-flake graphite closed extraction device. The device comprises an extraction device main body, an air guide and injection device, a filtration and slag removal device, a stirring and foam scraping device and a top cover lifting device, wherein the extraction device main body is provided with two slag removal openings and two graphite foam liquid outlets; the air guide and air injection device comprises an air inlet, exhaust pipes and exhaust holes; in a filtration device, two semicircle cone filter screens are symmetrically buckled on fixing hanging buckles in the middle of a vertical axis of a rotor, and the filter screens can be electrically lifted along with a top cover; the slag removal device comprises a slag removal opening and a residue removal opening; in a stirring device, tray impellers spread above the four exhaust pipes are fixed to the lower end of a vertical rotor; in a foam scraping device, two foam scraping plates are symmetrically fixed to the upper end of the vertical rotor; the electrically-driven lifting top cover is fixed to the upper end of the vertical rotor, and is occluded with the upper edge of the peripheral side of the extraction device main body during declining. By adoption of the device, the problem in high-purity, efficient, environment-friendly and energy-saving closed extraction of large-flake graphite is solved.