Abstract: A state space approach for the analysis of free vibration of piezoelectric laminated plate with delamination is presented. Firstly, the meshless state space formulation is derived by the modified H-R (Hellinger-Reissner) varitional principle and radial basis function. And then, the three-dimensional model of the piezoelectric laminated plate with a delamination is reduced by incorporating a nonlinear spring-layer model. The main advantages of the model are that the field nodes and the background grids are only used in each layer and the number of variables is independent of the layer number of the structure. In the plane of delamination the nonlinear spring-layer ensures the continuous transverse stresses and displacements in the undelaminated region by specifying the value of springs and avoids the possibility of material penetration phenomenon in the delaminated region.