Polyaniline/sodium alginate(PANI/SA) was successfully synthesized by oxidative polymerization of aniline using sodium alginate (SA) as soft template. The structure and morphology of the products were characterized by Fourier transform infrared spectrum (FTIR) and scanning electron microscopy (SEM). The electrochemical properties of the as-prepared PANI/SA were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (CD) test and electrochemical impedance spectroscopy (EIS) in 1 mol/L H2SO4 aqueous electrolyte. The results showed that the specific capacitance of the prepared PANI/SA increased firstly but decreased then with the increasing of the concentration of SA. The PANI/SA appeared as a network morphology intertwined with the nanofibers and showed a higher specific capacitance of 459.7 F/g with the SA mass fraction of 0.01%, which was an improvement over that of pure PANI(20.8%).