A cutting height adjusting system of a lawnmower constituted by a worn screw able to cause a lead screw nut to translate while carrying a mount for a cable (7) and by an eccentric member (8) connected to said cable (7) and hinged between the axle (O) of the lawnmower and the frame (A), such that a rotation of said eccentric member (8) coresponds to a tensile stress of the cable (7).