A series of MXene/HDPE and MXene/CNT/HDPE foams were prepared using high-density polyethylene (HDPE) as matrix and MXene and carbon nanotube (CNT) as modified fillers by regulating the decomposition temperature of azodicarbonamide (AC) though melt blending and gradient temperature moulding method. The effects of melt viscosity on the crystallization and cell growth of modified HDPE foams were investigated by Haker rheometer, X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and polarizing microscope (POM). The thermal conductivity, hydrophilic energy and the interface evaporation rate of fresh water and/or salt water of modified HDPE foam materials were tested by infrared thermometer, contact angle tester and xenon lamp evaporation meter to explore the effect of filler on the photothermal characteristics of HDPE foams. The results show that MXene decreases the melt viscosity of the HDPE-based foam materials, while CNT increases the melt viscosity of the materials; MXene and CNT do not have a significant effect on the crystal morphology of HDPE, but reduce the crystallinity of HDPE-based foam materials to a certain extent; however, both MXene and CNT could improve the thermal conductivity of the foams, and MXene improves the hydrophilicity of the foams. At the solar irradiation intensity of 1.5 kW/m2, when the mass fraction of MXene is 2%, the average evaporation rate of fresh water and/or salt water for MXene/HDPE foam material is 1.34 kg/(m2·h) and 1.21 kg/(m2·h), respectively, and the increase of pure HDPE cell material is 29.97% and 29.04%. The average evaporation rate of fresh water and brine of the HDPE foam is 1.53 kg/(m2·h) and 1.38 kg/(m2·h), respectively, and their evaporation efficiency are 39.97% and 35.60% higher than those of pure HDPE foam material.