Abstarct: In this research, the elastic analysis of shells made of heterogeneous materials will be provided. The geometry of considered shell is a complete sphere and its material is the functionally graded materials. The governing equations of considered shell are derived by the nonlinear plane elasticity theory for a thick sphere, and the boundary conditions and applied loads are include of two inner and outer surface pressure forces which are applied along radius on inner and outer surfaces of sphere, respectively. In the nonlinear elasticity theory or the large deformations theory, the deformations are significant with regard to thickness and sizes of the structure, thus nonlinear terms will be appeared in the kinematic equations. For the considered sphere, these nonlinear terms will turn the derived equations into a second-order nonlinear equations with variable coefficients. These nonlinear equations are solved analytically by using the perturbation theory. In the achieved results, the effect of loads, thickness of sphere and heterogeneous coefficents of materials on the displacements and stresses are investigated. Also the considered sphere is modeled and analyzed in the ABAQUS software by implementing the finite element method, then the numerical results are compared with analytical results which shows high accuracy and convergence between the solutions.