In this research, the theory of generalized thermoelasticity is used to investigate the plane harmonic waves reflection from a rotating semi-infinite elastic solid with a gravity field. The coefficients of reflection, which are the reflected wave amplitudes ratios to incident wave amplitudes, are calculated. The numerical solution is obtained and the graphic representation of the rotation and gravity fields of the on the coefficient of reflection is shown. In the presence and absence of rotation and gravity, comparisons are conducted with the predictions of the Lord-Shulman and dual-phase-lag models. The gravitational and rotational effects explain the reflection coefficient of waves on the free half-space surface.