The Poly(3,4-ethylenedioxythiophene)∶Poly(styrenesulfonate) (PEDOT∶PSS)films modified by the method of Dimethyl Sulfoxide (DMSO) was directly spin-coated on the PEDOT∶PSS anode interface layer, which made the performance of perovskite solar cells device has been greatly improved. Under the DMSO spin-coating speed of 5000 rpm, the power conversion efficiency of the device has reached up to 11.43%, which increases 29.15% compared with the device with an unmodified PEDOT∶PSS anode interface layer. The transmission spectra, surface morphology, conductivity of the PEDOT∶PSS films before and after modification were tested, and the external quantum efficiency curve and the J-V characteristic curve under illumination and dark were also tested to reveal the origin of the improvement of the device performance. The results show that, the conductivity of the modified PEDOT∶PSS film has been improved significantly, and thus the anode of the device can more efficiently extract and collect the charge carriers of holes. Compared with the device with unmodified PEDOT∶PSS, the short circuit current density of the modified device has been enlarged significantly that accounts for the higher power conversion efficiency.