In this paper, a simple method of UV-light irradiation treatment was employed to enhance electrical performance of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/poly(vinyl alcohol) blend fiber. It could be seen that fiber conductivity had significant increase after exposure to UV light (λ = 255 nm) under vacuum. Mechanism of UV-light irradiation on the improvement of electrical performance of blend fiber was investigated by FT-IR, Raman, XPS, and ESR spectroscopies. FT-IR spectroscopy revealed that UV irradiation decomposed chemical bonds of PSS chains, leading to cross-linking of PSS chains via recombination of free radicals. Raman results showed that PEDOT polymer chain transformed from benzoid structure to quinoid structure improving planarity of PEDOT polymer chains. ESR spectroscopy proved that fibers treated by UV-light irradiation had higher degree of charge delocalization across conjugated PEDOT backbone. Cross-linking of PSS chains formed multiple paths for better charge transportation among PEDOT-rich grains, which was responsible for conductivity enhancement in blend fiber. Our results demonstrated that UV-light irradiation could effectively improve the conductivity of PEDOT:PSS/PVA blend fiber by decomposition and cross-linking of PSS chains. Decomposition of PSS chains is favorable for better inter-connection between adjacent PEDOT chains, and cross-linking of PSS chains will provide higher degree of barrier-free path for charge transportation through π-conjugated PEDOT chains. Conductivity enhancement induced by UV-light irradiation is independent of fiber formation process thus allowing them to be candidate for broader applications.