The work aims to improve the hydrophobicity of plant fiber foam materials and explore the effect of hydrophobic modification on their various properties. With plant fiber and PVA as raw materials, F127 active foaming agent was used to prepare a mixed plant fiber foaming material. It was then impregnated with PDMS/n-hexane mixed solution for hydrophobic modification. The effect of hydrophobic modification on the properties of plant fiber foam materials was studied through scanning electron microscopy, infrared spectroscopy, thermogravimetric analysis, contact angle, mechanical properties, thermal insulation performance, cleanliness (Oil absorption) and other tests. The angle of the hydrophobic modified plant fiber foam material reached 154.2°, exhibiting superhydrophobicity. Compared with that before modification, its compressive strength (80% strain) increased from 187.43 kPa to 223.04 kPa, and there was no significant difference in compressive resilience (50% strain). The stability of hydrophobic plant fiber foam materials was improved in high humidity environments. Its static and dynamic buffering coefficients were 0.05 and 18.2, respectively. After heating for 60 minutes, the surface temperature only increased by 3.4 ℃, and its good absorption of xylene could reach 24.69 g. Hydrophobically modified plant fiber foam materials have good buffering, thermal insulation, and cleaning functions.