The present work describes the fabrication of yttrium iron garnet (YIG) nanofibers prepared via electrospinning method. The YIG nanofibers with diameters of around 80 nm were formed when calcinations temperature exceeded 750 degrees C. The morphology and magnetic parameters including saturation magnetization (M-s) and coercivity (H-e) of these samples dramatically change with variation of the annealing temperature. In particular, the M-s displays a steady increase from 3.1 emu/g at 700-21.5 emu/g at 1000 degrees C, and the H-e shows a different tendency that first increases to a maximum value of 140 Oe at 750 degrees C, and then reduce distinctly. Finally, the electron spin resonance spectra display strong asymmetry and broad linewidth that are highly affected by shape anisotropy, defects and the presence of trace amount second phase orthorhombic YFeO3 (o-YFeO3) in the YIG nanofibers.