In this work, fully transparent dual-layer channel self-aligned top-gate amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) are fabricated on glass substrates. Dual-layer channel is consist of indium gallium zinc oxide with different partial pressure of oxygen while sputtering. An oxygen-rich IGZO was deposited to control the threshold voltage and an oxygen-poor IGZO was then deposited to modulate device mobility. The device exhibited the excellent performances, including: a field effect mobility of 5.33 cm2/Vs, a suitable threshold voltage of 1.68V, a sub-threshold swing of 0.54V/dec and a high on/off current ratio. Furthermore, the devices also shows great stability under bias stress.