In this paper, an analytical model is developed to study the influence of initial hydrostatic stress and piezo elasticity on elastic waves in a piezoelectric layer embedded on a gravitating half space with slip interface. The piezo electric layer considered for this study is hexagonal (6mm) material. The problem is described using equations of linear elasticity with initial hydrostatic stress and piezo elastic inclusions. Displacement functions in terms of velocity potential are introduced to separate the motion's equations and electric conduction equations. The frequency equations are obtained by stress free and electrically shorted boundary conditions at the gravitating half space. The numerical computation is carried out for the PZT-4A material. The obtained results are presented graphically to show the effect of piezo elastic coupling and hydrostatic stress on the elastic waves.