The embodiments of the present invention disclose a touch stylus, a touch detection method and a touch detection system, which are suitable to be used for writing on a capacitive touch screen and can increase the success rate of touch. A method according to an embodiment of the present invention includes: receiving, by a sensing electrode, a square wave signal sent from a stylus tip of a touch stylus; performing a detection process on the square wave signal, by a sensing detection unit, the sensing detection unit having a clock synchronized with a clock of the touch stylus; determining, by a signal processing unit, whether a touch event occurs according to the square wave signal processed with the detection process; and calculating position coordinates of the touch event and reporting the position coordinates to a system control unit, by the signal processing unit, if a touch event occurs.