Taperlike Si nanowires (SiNWs) have been synthesized by annealing of high-density FeSi2 nanodots on (001) Si at 1200 °C in a N2 ambient. The tip regions of SiNWs are about 5-10 nm in diameter. The average length of the SiNWs is about 6 μm with aspect ratios as high as 150-170. A growth model based on oxide-assisted growth is proposed. The taperlike morphology may be caused by the passivation of the SiO2 coating layer, which results in the different levels of absorption of SiO along the length of the nanowires. The SiNWs exhibit a turn-on field of 6.3-7.3 Vμm and a threshold field of 9-10 Vμm. The excellent field emission characteristics are attributed to the taperlike geometry of the crystalline Si nanowires.