A key switch includes a rubber cone supported on a membrane circuit board inside a keyboard, a key base covered on the rubber cone to hold a vertically slidably key cap, a spring holder cap vertically slidably coupled to the key cap inside the key base to hold spring between the key cap and the spring holder cap, the key cap has two inner hooks respectively extended from two opposite sides of a bottom coupling frame thereof for engagement with the spring holder cap, the spring holder cap having outward hooks raised from the topmost edge thereof at two opposite sides for engagement with the inner hooks of the key cap, the rubber cone being compressed by the spring holder cap to trigger a contact at the membrane circuit board and the spring suddenly extending out to produce a click sound when the key cap is depressed.