The strike mechanism (1) of a watch includes a gong (21), which is secured by one end thereof to a gong-carrier (22) integral with a plate, a hammer (2) rotatably mounted on the plate for striking the gong (21) at predetermined times, a damping counterspring (5) for keeping the hammer at a distance from the gong (21) in an idle mode, and a spring (3) for driving the hammer. The drive spring includes one end (3b) secured to the plate and one end (3a) that is free to move. The spring is capable of being wound so that the free end (3a) of the spring drives the hammer (2) against the gong (21) in a strike mode to generate an acoustic sound. The strike mechanism further includes a stop member (10) on the path of the hammer drive spring in the direction of the gong for increasing the strike speed following contact of an intermediate part of the drive spring (3) in action against the stop member.