Polyacrylonitrile (PAN) nanofibers were prepared by an electrospinning technique, which were chemically modified with amidoxime groups. The silver nanoparticles were then synthesized on amidoxime modified PAN (OM-PAN), which was used for the photodegradation of methyl orange in aqueous solution. The SEM images showed that the average diameter of PAN nanofibers was below 200 nm. The SEM micrograph also showed that the silver nanoparticles were well dispersed on the surface of OM-PAN nanofiber mat. The micrograph also presented that the average size of silver nanoparticles was below 100 mu. The photodegradation study showed that the degradation of methyl orange in aqueous medium was increased as increased the irradaition time. The results illustrated that silver nanoparticles (Ag)/OM-PAN nanofiber mat degraded about 80 % of methyl orange within 6 h. The degradation efficiency was found to be pH dependent and maximum degradation was found at lower pH (about 90 % of dye is degraded at pH 2). The Ag/OM-PAN nanofiber dosage presented that the degradation of dye was increased as increased the catalyst dosage.