The influence of the abrupt density change near the limiter radius in Tokamak on the coupling of lower hybrid wave with grill is considered. It is discovered that the serious wave reflection, which exists in the region of the abrupt density change, would reduce the coupling efficiency of the grill. A standing wave is formed between the region of the abrupt density change and vacuum chamber wall by the reflected wave. The power and the energy flux spectra would be changed and more sensitive to the plasma boundary condition. In addition, the accessibility criterion of LH wave would be loosened.