PVA/[Gd(NO3)3+Yb(NO3)3+Er(NO3)3] composite nanofibers were fabricated by the combination of sol-gel method and electrospinning. Gd2O3:Yb3+, Er3+ upconversion nanofibers were obtained by the calcination of relevant composite nanofibers. The samples were characterized by using XRD, SEM, TG-DTA, FTIR and fluorescence spectroscopy techniques. The results show that the composite nanofibers are amorphous in structure, and Gd2O3:Yb3+,Er3+ upconversion nanofibers are cubic in structure with space group Ia3. The mean diameter of the composite nanofibers is 140nm. The Gd2O3:Yb3+,Er3+ upconversion nanofibers of 60nm in average diameter were acquired at 600℃. The water, organic compounds, nitrates in the composite nanofibers are decomposed and volatilized totally, and the weight of the sample keeps constant when sintering temperature is above 600℃, and the total weight loss percentage is 81%. The FTIR spectrum of the composite nanofibers is basically the same as that of the pure PVA, and Gd2O3:Yb3+, Er3+ upconversion nanofibers are formed above 600℃. In the excitation of a 980 nm continuous wave diode laser, the Gd2O3:Yb3+, Er3+ nanofibers emitt strong green and red upconversion emissions centered at 522nm, 560nm and 659nm, respectively. The green emissions are attributed to the transitions of 2H11/2/4S3/2→4Il5/2 energy levels of Er3+ ions, and the red emission is assigned to the transition of 4F9/2→4Il5/2 energy levels of Er3+ ions. In the course of Gd2O3:Yb3+, Er3+ upconversion nanofibers formation, PVA acts as an oriented template. When the composite nanofibers are sintered, PVA is decomposed and evaporated, and rare earth nitrates are also decomposed and oxidized and then Gd2O3:Yb3+, Er3+ nanoparticles are formed. And these nanoparticles are mutually connected to form the Gd2O3:Yb3+, Er3+ upconversion nanofibers.