In this paper, we investigate the doping effect on conductivity of poly(3,4-ethylene dioxythiophene):poly (styrenesulphonic acid)(PEDOT ∶PSS)and its influence on performance of polymer solar cell. The experiment demonstrates that the conductivity of PEDOT ∶PSS is improved obviously by doping polar solvent dimethyl sulfoxide (DMSO). The maximum of the conductivity is 1.25 S/cm when the doping concentration reaches 10 wt%, which increases about three orders of magnitude compared with the undoped. Based on doped PEDOT ∶PSS used as an anode buffer layer, the polymer solar cell (ITO/PEDOT ∶PSS/P3HT:PCBM/LiF/Al) shows an improvement of hole charge transport as well as an increase of short-circuit current density and a reduction of series resistance, owing to the higher conductivity of the doped PEDOT ∶PSS. Consequently, it improves the whole performance of polymer solar cell. The short-circuit current density (Jsc) of 11.09 mAcm-2, the open circuit voltage (Voc) of 0.63 V, and the fill factor (FF) of 63.7% are obtained under 100 mW/cm2 air-mass solar simulator illumination, yielding a 4.45% power conversion efficiency ().