A touch pen for a capacitive touch screen is provided. The touch pen includes a signal receiver conductor, a signal detecting and adjusting circuit, and a signal transmitter conductor. The signal receiver conductor receives a first touch signal from the capacitive touch screen. The signal detecting and adjusting circuit enlarges the first touch signal to a second touch signal having a standard intensity with a first magnification factor, a second magnification factor and a third magnification factor. The signal transmitter conductor issues the second touch signal to the capacitive touch screen. According to the second touch signal, the capacitive touch screen senses a position of a touch point of the touch pen.