The invention discloses an autoinflation floating body air shield dam gate anti-freezing device, which comprises a pneumatic water surface writhing mechanism, a hydrodynamic water surface writhing mechanism and a floating body mechanism. The pneumatic water surface writhing mechanism is used for spraying air within a first range, away from the water surface by a preset distance, below the water surface to enable the water surface to writhe so as to prevent the water surface from being iced; the hydrodynamic water surface writhing mechanism is used for spraying water within a second range, awayfrom the water surface by a preset distance, below the water surface to enable the water surface to writhe so as to prevent the water surface from being iced; and the floating body mechanism is usedfor suspending the pneumatic water surface writhing mechanism and the hydrodynamic water surface writhing mechanism to be within the corresponding range, below the water surface, of the preset distance. The water surface can be prevented from being iced, a gate is protected, clamping and fixing on a guiding rod are further achieved through inflation of an inner layer of a double-layer lock cylinder, thus the anti-freezing device is fixedly mounted at any position in a water body, and the defect that a traditional anti-freezing device cannot move along with the water level and consequently is prone to losing efficacy is overcome.