Electrospinning is an efficient method to prepare ultrafine fibers of polymer. In this article, we describe the fabrication of high quality polyethersulfone (PES)/sulfonated polyethersulfone (SPES) blend nonwoven membranes having possible application for water purification. All spun fibers were bead-free; raising the ratio of SPES to PES led to a reduction in fiber diameters, with an aggregated structure being formed. In order to precisely investigate the glass transition temperature (T-g) of the obtained membranes, modulated differential scanning calorimetry (MDSC) was used; the addition of SPES promoted a growth in T-g value. As the content of SPES increased, a two-step thermal degradation was observed in thermogravimetric analysis (TGA) curves. Compared to pure PES fibrous membranes, the mechanical properties of PES/SPES membranes were significantly improved, while the surface hydrophilicity of the blend membranes increased slightly.