The dynamic model of the micro laminated plates is developed with its boundary conditions through Hamilton's principle, based on the classical thin plate theory and taken into consideration of the size effect caused by the micro scale using the strain gradient theory. After choosing the proper mode functions for the boundary conditions of both simplesupport and cantilever, the first five orders of natural frequencies and the corresponding 3D mode shapes are achieved by the Ritz method, respectively. The effect of size effect on natural frequencies is studied. Eventually, the influence of the external voltage on the natural frequency is also examined.