Taken into account the curvature effects，we build a singleπ orbital tight-bi ndi ng model for armchair toroidal carbon nanotubes, from which the interaction matr i x elements have been derived by means of the wavefunction decomposition method. The electronic structures of armchair toroidal carbon nanotubes are studied, whi ch are dependent on both the torus radius and the tube radius. The energy spectr al transition is observed from the discrete to continuous ones, as the t orus radius and the tube radius are varied.