The orthotropic rectangular thin plate equations were transformed into the Hamiltonian system,and the corresponding infinite dimensional Hamiltonian operator was obtained with the method of separation of variables. Then the eigenvalues and corresponding eigenfunctions of the Hamiltonian operator were calculated,and the eigenfunction system was proved to be of symplectic orthogonality and completeness.Finally,with the symplectic superposition method,the analytical bending solutions of fully clamped orthotrop...