With the rapid development of industrialization, the deterioration of water resources, especially oily wastewater pollution, is becoming a worldwide threat, because it is severely harmful to biological and human safety. Recently, porous meshes with superhydrophilicity and underwater superoleophobicity have attracted significant attention due to their low oil adhesion and selective oil-water separation. However, simple, environmentally friendly, low-cost, multifunctional and facile scaled-up materials are still urgently in demand. Here, a natural polymer-based hydrogel prepared by konjac glucomannan (KGM) was coated on glass fabric, a kind of engineering material. The resulting hydrogel-coated glass fabric not only shows excellent performance of water removal from oil-water mixture but also can remove organic dyes and heavy metals in water simultaneously during the oil-water separation process. In addition, due to the strong hydration capacity, the DKGM hydrogelcoated glass fabric shows underwater ultra-low-oil-adhesive superoleophobicity to viscous oils, which means it is self-cleaning with respect to oils in an aqueous environment and can be easily recycled for long-term use. Importantly, the superhydrophilicity and underwater superoleophobicity of these hydrogel-coated glass fabrics were maintained under various harsh conditions. The low-cost, biodegradable and environmentally friendly preparation, resistance to harsh conditions and multifunctional applications properties make these hydrogelcoated glass fabrics hold great potential for purifying oily wastewater.