Polyvinyl alcohol(PVA)/[La(NO3)3+Mn(CH3COO)2] composite nanofibers were fabricated by electrospinning, and polycrystalline LaMnO3 nanofibers were prepared by calcination of the PVA/[La(NO3)3+Mn(CH3COO)2] composite nanofibers at 600oC for 10h. The samples were characterized by using thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffraction spectrometry(XRD), scanning electron microscopy(SEM) and Fourier transform infrared spectrometry(FTIR). The results show that PVA/[La(NO3)3+Mn(CH3COO)2] composite nanofibers are amorphous in structure, and pure phase LaMnO3 nanofibers are orthorhombic with space group Pbnm. The surface of as-prepared composite nanofibers is smooth, and the diameter is about 150nm. The diameter of LaMnO3 nanofibers is smaller than that of the relevant composite fibers. The surface of the LaMnO3 nanofibers becomes coarse with the increase of calcination temperatures. The diameter of LaMnO3 nanofibers is ca. 100nm, and the length is greater than 100????m. The mass of the sample remains constant when the temperature is above 450oC, and the total mass loss percentage is 94.6%. Possible formation mechanism of LaMnO3 nanofibers is preliminarily proposed.