Indium gallium zinc oxide (IGZO) is widely used in thin-film transistors (TFT) as an active layer due to its high mobility and transmittance. The amorphous n-type indium gallium zinc oxide thin-film transistors (IGZO-TFT) of bottom gate with high mobility were prepared, the active layer, source and drain electrode of the TFT were prepared by using magnetron sputtering method, and a low cost mask was used to control the size of the channel. The diffraction pattern and transmittance spectrum were measured by using X-ray diffraction and ultraviolet-visible spectrophotometer, respectively. The structural and optical properties of the IGZO thin film were studied. The dependence of active layer thickness on the performance was analyzed by testing the output characteristics and transfer property of IGZO-TFT. The field effect mobility of the IGZO-TFT reaches 15.6 cm2·V-1·s-1, and the on/off ratio is higher than 107.