A porous graphene/nano-tungsten powder/epoxy mixture is used as the acoustic absorption backing material to enhance the bandwidth of needle-type hydrophones. Using the KLM model, we found that thicker and higher-attenuation and medium acoustic impendence backings broadened the hydrophone bandwidth, enabling a flatter frequency response. Therefore, the new backing material should consider the above parameter characteristics. Finally, based on the above research findings, a needle-type hydrophone developed using the optimal new backing material achieved a 10.2 MHz bandwidth, which is consistent with the simulated value. Compared to needle hydrophones with air backing and copper rod backing, the bandwidth of the developed needle-type hydrophone was expanded by 410% and 75%, respectively, with a flatter frequency response within the bandwidth.