Due to their inherent crystalline properties piezoelectric actuators have a limited deformation. This intrinsic drawback deprives to exploit the potential of these actuators such as, high bandwidth and high resolution in applications that require large displacement range. To overcome this limitation, classical as well as systematic approaches were proposed to design amplification mechanisms. The classical approach leads to empirical mechanisms which are not trivial and needs much experience and intuition. In contrast, systematic approach uses topology optimization method which permits to automatically derive optimal designs that can satisfy specified performances and imposed constraints simultaneously, this with a reasonable time and cost. This paper proposes the design of a mechanism devoted to amplify the displacement of a piezoelectric actuators (PEA). Based on the SIMP topology optimization method, the approach permits to derive a design with a displacement amplification ratio of 4.5, which is higher than with the existing method of Rhombus mechanism. Both finite element (FE) simulation and experimental results confirm and demonstrate the efficiency of the approach.