LaMnO3+delta nanofibers have been prepared by electrospinning. The nearly 70% of Mn atoms is Mn4+, which is much higher than that in the nanoparticles. The average grain size of our fibers is approximately 20 nm, which is the critical size producing the nanoscale effect. The nanofibers exhibit a very broad magnetic transition with T-c approximate to 255 K, and the T-c onset is around 310 K. The blocking temperature T-B is 180 K. The sample shows weak ferromagnetic property above the T-B and below T-c and superparamagnetic property near the T-c onset. The resistivity measurements show a metal insulator transition near 210 K and an upturn at about 45 K.