Abstract. Polythiophene nanoparticles prepared by W/O microemulsion method were found to be photocatalytically active for degradation of Orange II dye and methyl Orange. During the photodegradation of Orange II and Methyl Orange as organic dyes in UV/H₂O₂and UV irradiation systems using polythiophene nanoparticles as photocatalyst, it is exhibiting significant photocatalytic activity towards to double dyes in UV and UV/H₂O₂system. the diameter of spherical polymer nanoparticles is 100±20 nm which was characterized by TEM with good dispersity. Furthermore, its photocatalytic efficiency for degradation of Orange II and Methyl Orange under UV irradiation is 2.54 and 1.95 times higher than normal polythiophene composites relatively. According to the testment by Accelerated Surface Area and Porosimetry System, The true cause lay in the fact that the specific surface area of Polythiophene nanoparticles is 106.6 m2/g compared to normal Polythiophene is 24.2 m2/g, This conjugated polymer characterized by FTIR spectroscopies before and after photocatalytic reactions shows reliable chemical stability. In addition, it held excellent recovery ability and kept up their catalytic activity with indistinctive drop after six repeated utilization.