Organic light-emitting devices have become the potential mainstream te chnology of the next generation flat panel display and solid state lighting with unique advantages such as light weight,high brightness,flexibility,wide view ing angle and fast response.Hole injection improvement in organic light-emitti n g devices with PEDOT:PSS doped MoO_3as a hole inject layer on indium tin oxide ( ITO) has been demonstrated.The luminance and the current efficiency are signifi cantly enhanced,as well as the turn-on voltage is reduced by 0.5V compared to undoped device.Results of AFM,transmission and hole-only devices studies reve a l that the enhanced performance of devices is attributed to the modification of the ITO surface,increased the transmittance of green light area and the reduced resistance of hole injection layer by the insertion of the PEDOT:PSS:MoO_3lay er between the ITO and hole-transporting layer.