Effects of annealing temperature (600-750 degrees C) on crystalline structure, the morphology and piezoresponse hysteresis loops of BaTiO3 nanofiber sprepared by electrospinning are characterized by X-ray diffraction, scanning electronic microscopy, transmission electron microscope and piezoresponse force microscope. When the annealing temperature is 700 degrees C, the nanofibers become smoother and have a diameter of 100-300 nm. Meanwhile the typical butterfly-shaped amplitude loop and 180 degrees phase change represents the best ferroelectric and piezoelectric properties at 700 degrees C. So the 700 degrees C was found to be optimum for good piezoelectric characteristics at annealing temperature of 600 degrees C-750 degrees C. In order to give more clear evolution of domain states at different external fields, the three dimensional topographic and phase images of the nanofiber at different temperatures are observed by piezoresponse force microscope. The 90 degrees domain switching is observed during heating from room temperature to 125 degrees C and the domain switching tends to be stable when the temperature exceeds a critical value. The thermal stress due to the high temperatures is responsible for switching mechanism from the perspective of equilibrium state free energy. This work suggests that the temperature variation should be considered while designing the ferroelectric devices based on one dimensional material.