A stylus includes a casing comprising an opening, a push rod disposed in the casing, a pen head fixed on an end of the push rod, a reflector coupled to the push rod, and a linkage mechanism disposed in the casing. At least a part of the pen head is exposed of the casing. An end of the linkage mechanism is fixed on the casing. The linkage mechanism connects reflector to the push rod, such that when the pen head is pushed into the casing, a moving distance of the reflector is greater than that of the pen head, and the reflector is exposed of the opening.