Highly aligned amorphous silica nanowires were prepared on silicon substrate. The products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and selected-area electron diffraction (SAED). The photoluminescence (PL) spectrum of silica nanowires showed strong blue emission peaked at 401 and 440nm under 274nm excitation wavelength. The growth mechanism of the nanowires was proposed.