The invention discloses a hot air variable pressure discharging hot concentrated waste water fluidizing, crystalizing and drying system and method. According to the hot air variable pressure discharging hot concentrated waste water fluidizing, crystalizing and drying system and method, air is heated by a first heat exchanger through an air inlet unit into hot air, the hot air serves as carrier gasand is fed via the air inlet of a fluidizing, crystalizing and drying tower to blow spherulite filler between the inner tube and the outer tube of a drum into a micro-floating fluidized state; concentrated waste water which is preheated by a preheater and heated by a second heat exchanger is distributed to atomizers on the inner tube of the drum and atomized and sprayed onto the surface of the spherulite filler for heat and mass transfer with the hot air, water is taken away by the hot air to obtain wet saturated air, and salt inside the concentrated waste water is crystalized, dried and hardened on the surface of the fluidized spherulite filler; along with rotation of the inner tube and motion of the hot air, the salt is ground among the spherulite filler, collides, falls off and is thensettled down by the screen of the outer tube to a crystal collecting hopper at the bottom of the fluidizing, crystalizing and drying tower, the wet saturated air is compressed, transfers heat via phase exchange through a preheater and is condensed into dehumidified air and then discharged in a variable pressure mode through an air expansion unit.