In this paper has been studied the wave equation in some non-classic cases. In the rst case boundary conditions are non-local and non-periodic. At that case the associated spectral problem is a self-adjoint problem and consequently the eigenvalues are real. But the second case the associated spectral problem is non-self-adjoint and consequently the eigenvalues are complex numbers,in which two cases, the solutions of the problem are constructed by Fourier method. By compatibility conditions and asymptotic expansions of the Fourier coe cients, the convergence of series solutions are proved. At last series solution are established and the uniqueness of the solution is proved by a special way which has not been used in classic texts.