A plastic optical touch panel applicable for large-scale flexible display is demonstrated based on a vertical directional coupling between arrayed channel waveguides and a flexible planar waveguide. When a contact force is applied to the surface, the flexible planar waveguide is bent toward the channel waveguide, and then, the guided mode in the channel waveguide is coupled into the flexible planar waveguide, causing an output power drop. An index-matching liquid is used to fill the gap between the channel and the flexible planar waveguide in order to enhance the transparency of the waveguide touch panel. By applying a force of 1.0 N, the output intensity is decreased by 17 dB, which is sufficiently large for producing a contact signal.