Abstract: For the wide use of micro-spectrometer in diverse applications, its core device,torsion-type micromachined scanning gratings, were designed, fabricated and characterized. In order to obtain large scanning range and low resonant frequency at low driving voltage, the structure without additional starting electrodes was designed and studied by silicon-on-insulator (SOI) fabrication technology. The micromachined scanning gratings fabricated by SOI wafers were characterized, which prove that the micromachined scanning gratings has good modulation performances. The maximum deflection angles can reach 4.8, corresponding to a total optical scanning range of 19.2at a driving voltage of 25 V.