The toner display by an electrical movement of conductive toner has been investigated. The display cell consists of two transparent electrodes coated with the charge transport layer (CTL) and a spacer. The conductive toner and white particle are placed in this cell. The toner movement is controlled by the external electric field applied between two transparent electrodes. The conductive toners on the anode electrode are charged positively by hole injection from the CTL and move to the cathode electrode. They are fixed on the CTL on the cathode by an electrostatic force across the CTL to display a black image. The toners can be put back to the counter electrode by applying a reverse electric field, and a white image is formed.In toner display, the charge transport layer has the role of the hole injection from anode electrode to toner and blocking hole from a toner to the cathode electrode. It is necessary to do the existence of the Schottky barrier at the ITO/CTL/toner. In this paper, the charge injection is investigated by the measurement of I-V characteristic for ITO/CTL/toner sample. By using three kinds of charge transport material (CTM), an ionization potential of CTM is affected to the property of charge injection between electrode and toner. It is concluded that the contrast of display depends upon the ionization potential of CTM.