Fe (III)-amidoximated PAN fiber complex was prepared and used as a heterogeneous photo-Fenton catalyst for the oxidative degradation of Reactive Red 195 in water. The nature and concentration effect of inorganic salts on the dye degradation was investigated. Moreover, UV-Vis spectrum was also used to examine the decomposition process of the dye in the presence of the salt. The results indicated that the existence of the inorganic salts limited the photocatalytic degradation of the dye in water. Na2SO4 shows more strong inhibition effect on dye degradation than the other salts at the same conditions. UV-Vis spectrum demonstrated that the decomposition of the aromatic rings in the dye molecules was also reduced in the presence of the salt.