System for fixing rotary die cutters in die cutting machines for cutting laminar material includes a fixing means between the die (1) and a die-holder surface or cylinder (2) around which the die (1) is arranged, wherein the a fixing element include a plurality of bolts (3) actuated by an actuator (5) housed inside a hollow body (8) fixed to the die-holder cylinder (2) in order to provide for a rapid fixing of the rotary die to the die-holder cylinder.