Using the electrochemical polymerization dye sensitization(ECDS) method, polyaniline (PAn),which is used as top region material in solar cells, is sensitized with direct blue dye(DS), and sensitized Al grid/DS-PAn/n-Si/Al heterojunction solar cells is prepared by ECDS. Influences of the ECDS on the absorption spectrum and the junction characteristics of the solar cell were discussed, and the output characteristics were measured. The results show that the absorption spectrum of the sensitized PAn films is much wider and stronger in Vis-range; the diode quality factor is about 6.3 and the height of latent barrier potential of p-n junction is 0.89 eV; the short-circuit current and the conversion efficiency of sensitized DSPAn/Si heterojunction solar cells are greatly improved, which the short-circuit current can increase 6 times,the fill factor is 57% and the efficiency can reach 1.42% under the illumination of 37.2 W/m2 , respectively.