Dye pollution in water environment is a significant threat to ecological and human health, and its removal is very important yet challenging. Magnesium silicate-based materials have proven to be good adsorbents for dye wastewater treatment. In consideration of recycling and practicability, flexible and robust magnesium silicate fiber membrane (MgSiFM) is prepared for the first time via hydrothermal reaction using electrospun flexible SiO2 fiber membrane as silicon template. The preparation process is efficient, low cost and easy to scale-up. MgSiFM shows high tensile strength (5.52 MPa) and good mechanical stability. Moreover, the BET surface area of MgSiFM is measured as 463.4m(2)/g, which is similar to the reported powdery magnesium silicate-based materials. As expected, MgSiFM shows excellent adsorption capacity of 609.75 mg/g for cationic dye methylene blue (MB) with good recyclability. In particular, unlike powdery MgSi adsorbents, MgSiFM could act as a filter membrane for continuous and fast MB removal. The filtration performance is better than commercial nylon-6 microfiltration membrane and MgSi coated electrospun polymer fiber membrane. This work demonstrates a novel and facile strategy for the preparation of flexible magnesium silicate fiber membrane, which exhibits promising potential in practical wastewater treatment.