PVP/[Ba(CH3COO)(2) + Y(NO3)(3) + Er(NO3)(3)] composite nanofibers were prepared via electrospinning, and then mixed oxide nanofibers were obtained by calcining the composite nanofibers in air, and finally Ba4Y3F17:Er3+ nanofibers were successfully synthesized by fluorination of the as-prepared mixed oxide nanofibers used as precursor via a double-crucible method applying NH4HF2 as fluorinating agent. X-ray diffraction (XRD) analysis reveals that Ba4Y3F17:Er3+ nanofibers are pure rhombohedral phase. The diameter of Ba4Y3F17:Er3+ nanofibers is 84.3 +/- A 4.9 nm under the 95 % confidence level. Upconversion emission spectra analysis manifests that Ba4Y3F17:Er3+ nanofibers emit strong green and weak red upconversion emissions centering at 523 (H-2(11/2) -> I-4(15/2)), 541 (S-4(3/2) -> I-4(15/2)) and 652 (F-4(9/2) -> I-4(15/2)) nm, respectively, and the emitting colors of Ba4Y3F17:Er3+ nanofibers are located in the green region in CIE chromaticity coordinates diagram. The optimum doping molar concentration of Er3+ ions is found to be 9 %. Moreover, the formation mechanism and upconversion luminescence of the Ba4Y3F17:Er3+ nanofibers are also investigated. This novel preparation technique can be applied to prepare other rare earth fluoride one-dimensional nanomaterials.