The invention provides a technology for preparing a sound absorption material which is of a composite hole structure and is broad in sound absorption frequency through waste plastic. The technology specifically includes the processes of mixing, foaming, perforating, back cavity creating and the like. The technology is characterized in that after foaming, perforating, semi-perforating and back cavity treatment are conducted, sound absorption material hole channels are arranged in a criss-cross manner, the product is endowed with good low-frequency, medium-frequency and high-frequency broadband sound absorption effects, and the sound absorption frequency range of the material is greatly enlarged; the machining process is simple and easy to conduct, three waste is not generated, and the finished product can be recovered, re-machined and recycled after being abandoned; and the manufacturing technology is low in construction cost, the engineering installation is simple, the overall engineering thickness is generally 1 cm to 3 cm, the relative density is about 0.50 ton/m<3>, and the technology is suitable for establishing and use of sound absorption facilities of high-speed rails, city elevated roads, bridges, highway tunnels, building ceilings and the like.