The invention discloses a crystallization tower for gas-gas reaction. The crystallization tower comprises an upper seal head, a tower body and a lower seal head, wherein a gas outlet is formed in the upper seal head; a gas inlet and a material outlet are formed in the lower seal head; the tower body comprises a cooling section and a crystallizing section from bottom up; a heat removing assembly is arranged in the cooling section; a tower tray is arranged in the crystallizing section; the tower tray comprises a tower tray plate, a lifting lug fixed on a lower surface of the tower tray plate, and a crystallization column movably connected to the lifting lug. The crystallization tower provided by the invention has a large surface area capable of being attached with crystal substances, has crystals easy to remove and stack on the tower tray, is suitable for the crystallization process of ammonium hydrosulfide during acid water treatment in a refinery plant, and is especially suitable for the separation process of hydrogen sulfide in an acid gas containing carbon dioxide.