Graphene foams (GFs) prepared via a hydrothermal method can be vacuum-dried directly without the need for freezing by adding naphthalene to the graphene hydrogels. By optimizing the GF preparation process, it is also possible to adjust the GF's dielectric properties by varying the amount of naphthalene added. Based on the comparison results, it was observed that controlling the addition of naphthalene could also modify the internal structure of GF and effectively regulate its dielectric properties. GF-80, synthesized with 80 g of naphthalene, exhibited exceptional microwave absorption (MA) performance. At a mass content of only 2% and a matching thickness of 3.38 mm, a minimum reflection loss (RLmin) of -55.89 dB was achieved. Moreover, GF-80, with a thickness of 2.31 mm, was shown to achieve a bandwidth of RL less than -10 dB across 6.88 GHz.