Taking the laser diode as the light source, the traditional inner structure of touch screen is improved using a light pipe with microstructures. The single row of LED is replaced by a combination of the laser and the light pipe. Light pipe uses PMMA as the material, of which the refractive index n2=1.49. In the total reflection conditions, the geometric parameters of the light pipe′s micro-structure can be solved by a certain equation. The optical and mechanical models of the light pipe are established respectively, and the results show that this proposed design method achieve high resolution ratio and large size of the touch screen.