The porous carbon nanofiber mats were prepared by carbonization of electrospun polyacrylonitrile (PAN)/polymethylmethacrylate (PMMA) composite nanofibers and used as electrode materials for supercapacitor. The surface morphology and pore feature of the porous carbon nanofiber mats were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analysis. Cyclic voltammetry and chronopotentiogram methods were used to study the electrochemical properties of the porous carbon nanofiber mats as electrode materials for supercapacitor. Results showed that the porous carbon nanofiber mats had a good capacitance performance. The specific capacitance of the porous carbon nanofiber mats prepared at PAN/PMMA = 7:3 was 140.8 F g(-1). At a current density of 10 A g(-1), the specific capacitance of the porous carbon nanofiber mats prepared at PAN/PMMA = 7:3 only decreased by 4.6% after 10000 charge/discharge cycles. Therefore, the porous carbon nanofiber mats prepared at PAN/PMMA = 7:3 would be excellent electrode materials for use in supercapacitors.