Abstract: Reduced graphene oxide (RGO) and melamine sponge (MS) were utilized as loading and substrate materials to address the freshwater resource crisis. A mushroom-shaped graphene/melamine sponge composite photothermal water evaporation material (MRMS) was created to increase evaporation rate and decrease heat loss. It was investigated how the material's structure affected how well it performed in photothermal evaporation. The factors investigated include the ratio of total evaporation surface area to projected footprint area (expressed as EAI value), height of the bottom cylinder for water transportation, and the ratio between photothermal area and water absorption area (PAI value). The experimental results indicated that a MRMS formed by a top cylinder, 7 mm in height and 20 mm in diameter, and a bottom water conveying cylinder, 12 mm in height and 11 mm in diameter, showed the best photothermal evaporation performance. Under 1 sun illumination, the evaporation rate reached a maximum value of 2.41 kg·m⁻²·h⁻¹, with an evaporation efficiency of 91.53%. Characterization experiments on the optimal performance material, along with assessments of its continuous usage performance and salt resistance, demonstrate that the material exhibits stable continuous operational capability and salt resistance, showing application prospect in the field of seawater desalination.