The cantilever beam hydrophone can receive low frequency underwater acoustic signals in resonant frequency band, which can not only improve the sensitivity but also obtain superior detection performance compared with the traditional hydrophones, and has a broad application prospect in the field of marine engineering. This article designs a novel cantilever beam hydrophone based on acoustic metamaterials. First, the negative equivalent principle of the metamaterials and the effects of material parameters on resonant frequency are studied, and the method of reducing the resonant frequency of the cantilever beam hydrophone is obtained. On this basis, the first-order natural frequencies of single copper beam, three-layer copper-rubber beam and five-layer copper-rubber beam are analyzed, and the three-layer composite structure is selected to complete the design of the metamaterial cantilever beam hydrophone according to the practical requirements. The simulation analysis results show that the hydrophone designed in this paper has a lower resonant frequency than the conventional cantilever beam hydrophone with the same dimensions.