The present methodology of active vibration control has been developed for an optimum placement of actuators in the rectangular plate. The main aim of this work is modelling and analyze of smart structures under harmonic loading and influence of the Macro-Fiber actuators placement and size on the response of this structures. The development of smart structure technology offers great potential in the field of active vibration control and noise control of structures in different fields of application, such as aerospace, civil, and mechanical engineering. During the past few years, piezoelectric materials have been extensively used as actuators and sensors for noise and vibration control. This new structural concept requires the use of sensors and actuators for controlling the mechanical behavior of structural systems when using the converse piezoelectric effect to induce control forces and moments. Due to increasing interest in the design of complex smart structures with piezoelectric actuators and the need for fast and simple implementation of piezoelectric control systems, technology developers are beginning to provide more convenient tools to model smart structures. In this work, MFC actuators are used for the modeling of piezoelectric actuators, as an innovative actuator that offers high performance and flexibility in a cost-competitive device. Simulation and numerical computations of smart structures are performed in ANSYS 11.0 environment. The applied voltage is modelled as a thermal load according to thermal analogy for MFC actuator. According to numerical researches of smart structures, maximal reduce of vibration was achievement by the placement and direction of MFC actuators depended of mode shapes. Finally numerical results in terms of the harmonic response of smart structures with surface bonded MFC actuator demonstrates the validity of this method, which can be used for implementation of piezoelectric control system.