Micro linear actuators are applied to many precision fields such as ultra-precise positioning, precision manufacturing, optics, etc. The design of a micro-linear actuator is presented in this paper. The micro linear actuator includes a stacked piezo and a novel flexure-based differential amplifier mechanism. Stiffness, one of the most important factor to the resolution, is considered in the design step via an optimization problem using both analytical and finite element methods. The simulation of the designed actuator is also presented in the paper. Two problems, contact and strain-electricity coupling, are analized based on the ANSYS model to get the relation between the displacment, the voltage and the load applied on the actuator .