The invention relates to a chromium slag solidification gelling polymer. The polymer is an inorganic polymer gel formed through mutual connection of -Si-O-Al-O- bonds via a condensation polymerization reaction of geopolymer particles. The polymer comprises a zeolite phase composed of natrolite formed through a geopolymerization reaction, and a CSH mineral phase composed of calcium silicate hydrate and calcium aluminate generated through a hydration reaction. Most hexavalent chromium ions are solidified in the zeolite phase, and a small amount of hexavalent chromium ions are solidified in the CSH mineral phase, so the gelling polymer realizes immobilization of chromium ions in a geopolymer solidified body in an amorphous form. The chromium slag solidification gelling polymer is prepared through processing chromium slag, blast furnace slag and fly ash as raw materials by using a composite exciting agent composed of sodium hydroxide and water glass. A preparation method of the chromium slag solidification gelling polymer is simple to operate, and the gelling polymer prepared in the invention has good mechanical performances, can reduce the environmental pollution problem caused by piling of the blast furnace slag and the fly ash, and also can effectively prevent the leaching behavior of chromium ions in the chromium slag.