In order to obtain upconversion nanofibers materials of a new morphology,PVP/[Y(NO3)3+Al(NO3)3+Er(NO3)3+Yb(NO3)3] composite fibers were prepared by electrospinning,and Er3+,Yb3+:Y3Al5O12(Er3+,Yb3+:YAG for short) upconversion nanofibers were fabricated by calcination of the as-prepared composite nanofibers. Thermogravimetry and differential thermal analysis (TG-DTA) revealed that the water,organic compounds and nitrate salts in the composite nanofibers were decomposed and volatilized totally,and the weight of the sample kept constant when temperature was above 550 ℃,and the total weight loss percentage was 90.2 %. X-ray diffraction (XRD) results showed that the composite nanofibers were amorphous in structure,and pure phase Er3+,Yb3+:YAG nanofibers were obtained by calcination of the relevant composite fibers at 900 ℃ for 10 h. Fourier transform infrared spectrometer (FTIR) analysis manifested that crystalline Er3+,Yb3+:YAG upconversion nanofibers was formed at 900 ℃. Scanning electron microscope (SEM) analysis indicated that the diameter of Er3+,Yb3+:YAG upconversion nanofibers was about 75 nm,and the length was greater than 100 μm. Upconversion emission spectra showed under the excitation of a 980 nm continuous-wave diode laser,Er3+,Yb3+:YAG nanofibres emitted green and red upconversion emissions centered at 522,554 and 650 nm,respectively. The green(522 nm and 554 nm) and red(650 nm) emissions were attributed to the transitions of 2H11/2/4S3/2→4Il5/2 and 4F9/2→4Il5/2 energy levels of Er3+ ions. The formation mechanism of the Er3+,Yb3+:YAG nanofibers were preliminarily discussed. This method could be applied to prepare the other rare earths garnet-typed compound nanofibers.