A mechanism for setting a fuse, applied to the structure of a firearm 5, includes a setting device 2, adapted to program the fuse, the setting device 2 being fixed to a support structure 13 and having a reference portion 21 and a setting portion 22, rotating around the longitudinal axis of the fuse, adapted to set the fuse of a cartridge. The setting mechanism includes a support structure, the support structure supports a control device of the position of the setting device 2, formed by a movable equipment 31 from an actuator of a vertical movement 34 and from an actuator of a horizontal movement 35. The actuators are able to move along a horizontal “X”-axis of the support structure, along a vertical “Z”-axis, the same movable equipment 31 for the positioning of the setting device 2, with respect to the cartridge, kept in a predetermined position.