Abstract: These series works are concentrated on finding the general solutions in smart materials and structures. In order to find the solutions of a piezoelectric cantilever beam under different kinds of load conditions, the semi-inverse method is used. As the first part of all, the present paper deals with a piezoelectric cantilever beam subjected to a couple of forces. Some important parameters of the electro-mechanical fields are obtained and discussed. Several distribution curves such as stress and electric potential for material PZT (i.e. Pb(Ti_0.48Zr_0.52)O₃) are given. It should be pointed out that the material is functionally gradient in density.