The invention discloses an outdoor waterproof weather-proof wave-absorbing material and a preparation method thereof. The outdoor waterproof weather-proof wave-absorbing material is prepared by using a porous polyurethane sponge wave-absorbing material as a matrix, and coating a layer of completely closed flame-retardant rainproof coating on the outer surface of the matrix, wherein the flame-retardant rainproof coating is prepared from the following components in parts by weight: film forming matter: 28-30 parts of fluorocarbon emulsion and 26-32 parts of pure acrylic emulsion, pigment packing: 4-6 parts of titanium dioxide, fire retardants: 8-10 parts of aluminum hydroxide, and 5-8 parts of ammonium polyphosphate, 0.4-0.5 parts of a dispersing agent, 0.4-0.5 parts of a defoaming agent, and 15-27 parts of deionized water. The outdoor waterproof weather-proof wave-absorbing material has the characteristics of flame retardance, rainwater prevention and weather resistance.