Metamaterials demonstrate a series of unique properties in which natural materials do not have, and these properties have powerful manipulations to electromagnetic field, acoustic field and other physical fields. Being capable of absorbing sound wave and electromagnetic wave in broadband range, a multifunctional metamaterial composed of the multisized Helmholtz resonators and multisized metal resonators, is designed. The results show that the device could achieve an acoustic coefficient of more than 0.8 in the 690~927 Hz region and a microwave absorption over 80% in the 9.11~11.10 GHz range. The multifunctional metamaterials proposed are capable of absorbing both acoustic and electromagnetic waves with broadband and high efficiency and have potential applications in the aspects of noise pollution prevention and electromagnetic protection.