A touch input system including a stylus and a display device is provided. The stylus includes a battery module, a touch portion, a transducer module and a RF transmitting module. When a contact pressure is acted on the touch portion, the touch portion is electrically connected to the battery module by the contact pressure and emits a light signal. The display region receives and reacts to the light signal, and the contact pressure is transformed into an electrical signal by the transducer module. The RF transmitting module is electrically connected to the transducer module and transmitting the electrical signal. The display device includes a display region and a RF receiving module.