The invention relates to a high-elastic barrier foam and a preparation method thereof. The high-elastic barrier foam comprises a base layer, a barrier layer and a reinforcing layer which are thermallyfused into a whole in sequence, wherein the base layer is prepared from, by weight, 85 to 95 parts of polyether polyol, 20 to 35 parts of diphenylmethane diisocyanate, 1 to 2 parts of a foaming agent, 0.2 to 0.7 part of a catalyst, 3 to 5 parts of a flame retardant, 3 to 5 parts of a waterproof agent and 1 to 6 parts of silicone oil, and the hydroxyl value of the polyether polyol is 75 to 135; the barrier layer is prepared from, by weight, 30 to 45 parts of EVA, 4 to 6 parts of talcum powder, 6 to 8 parts of lime powder, 10 to 20 parts of triethyl phosphate, 32 to 42 parts of epoxy modified organosilicone resin powder, 10 to 12 parts of a styrene-acrylic emulsion and 0.3 to 1 part of a sodium polycarboxylate dispersing agent; and the reinforcing layer comprises, by weight, 90 to 95 partsof polyurethane and 5 to 10 parts of magnesium hydroxide. The tensile strength, the elongation at break, the tearing strength and other properties of the foam are remarkably improved, and meanwhile, the foam has a certain barrier effect, so that the application range of the foam is expanded, and the product performance is improved.