18–19‐MeV He++axial channeling in Si has been measured by the conventional single‐alignment method. In the backscattering spectrum, a shift of the resonant nuclear scattering peak to high‐energy side was observed when an axial channeling occurred. Moreover, the peak shift became maximal for about critical‐angle incidence of He++. These are direct evidences that the high‐energy‐loss fraction of channeled ions is considerably responsible for forming a backscattering spectrum.