PVP/[Ba(CH3COO)(2) + Y(NO3)(3) + Er(NO3)(3)] composite nanofibers were prepared via electrospinning, and then the mixed oxide nanofibers were obtained by calcination of the above composite nanofibers. BaY2F8:Er3+ nanofibers were successfully fabricated via a double-crucible fluorination method by using the prepared mixed oxide nanofibers as precursor. X-ray diffraction analysis reveals that BaY2F8:Er3+ nanofibers are pure monoclinic phase with space group of C2/m. The diameter of BaY2F8:Er3+ nanofibers is 159.9 +/- A 15.9 nm under the 95 % confidence level. Upconversion fluorescent spectroscopy analysis manifests that BaY2F8:Er3+ nanofibers emit strong green and weak red upconversion emissions centering at 523 (H-2(11/2) -> I-4(15/2)), 540 (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 BaY2F8:Er3+ nanofibers are located in the green region in CIE chromaticity coordinates diagram. The optimum doping molar concentration of Er3+ ions in the BaY2F8:Er3+ nanofibers is found to be 5 %. The formation process and upconversion luminescence mechanism of the BaY2F8:Er3+ nanofibers are also studied. This novel preparative technique can be applied to fabricate other rare earth fluoride one-dimensional nanomaterials.