A key structure of a keyboard includes a keycap, a scissor connecting mechanism, a conductive circuit board and a bottom plate from top to bottom, wherein a projection is arranged between the scissor connecting mechanism and the conductive circuit board; when an optional position of the periphery of the keycap is pressed, the scissor connecting mechanism is in contact with the projection before the conductive circuit board or the bottom plate below the scissor connecting mechanism; and if the optional position of the periphery of the keycap continues being pressed, the scissor connecting mechanism positioned on one side of the pressed point is bent and deformed by using the projection as a fulcrum and is in contact with the conductive circuit board.