Poly(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methanol)/carbon fiber composite material (PDHDM/CF) was prepared via a simple electrodeposition method. The CF core and the PDHDM shell formed a 3-D PDHDM/CF core/shell structure composite. The PDHDM/CF was characterized by FT-IR spectroscopy, UV–vis spectra, SEM, cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscope techniques. Compared with the PDHDM deposited on glass carbon electrode (PDHDM/GC), PDHDM/CF exhibited a remarkable specific capacitance of 280Fg −1 at a scan rate of 10mVs −1 , which was nearly three times that of the PDHDM/GC. The specific capacitance of assembled symmetric supercapacitor based on PDHDM/CF reached 27.35Fg −1 at 0.5Ag −1 and the energy density was 6.38Whkg −1 at a power density of 3.9kWkg −1 . These results indicated that the PDHDM/CF was a promising electrode material for the flexible supercapacitors application.