A crosslinked nanofibrous cation exchange membrane with high ion permeability and robust mechanical properties was fabricated by electrospinning. Copolymer, poly(sodium styrene sulfonate-co-2-hydroxyethyl methacrylate), was selected as the electrospun material. Fourier transform infrared spectroscopy, H-1-nuclear magnetic resonance, and scanning electron microscopy were employed to characterize the copolymer and nanofibrous mat. After a series of preliminary experiments, the proper solvents and their ratio, H2O/tetrahydrofuran/N,N-dimethylformamide (2/1/3 vol/vol/vol), was selected and the electrospinning optimal parameters were determined by orthogonal experiments. Formaldehyde vapor was employed to crosslink the mat. It was observed that the water sorption decreased from 47.9% to 18.4% as the crosslinking time increased from 20 to 32 h. The robust mat with the high tensile strength of 4.85 MPa and 40% elongation at break was obtained at 28 h. The permselectivities of Na+, K+, and Ca2+ were 89%, 85%, and 81%, respectively. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45541.