The invention relates to a fine positioning system using an inertial motor based on a mechanical amplifier, that comprises a first amplified inertial sub-assembly (20) including a mechanical amplifier (1), a piezo-active member (2) and a counter-mass (3). A second relative drive sub-assembly (21) includes a clamp (15) and a clamped member (24) attached to the first amplified inertial sub-assembly (20). Asymmetric excitation cycles of the first inertial sub-assembly generate impact forces and movements amplified in a driving direction (z), thus resulting in sliding and adhesion successions of the clamped member in the clamp in order to generate a relative translation movement of the points A and B relative to the point D. The mechanical amplifier (1) increases the step size and reduces the supply inrush currents. Fine and dynamic positioning of the point B relative to the point D can be achieved with augmented strokes using the amplifier (1).