In this paper, a combined model was proposed for reflection from a discontinuity and for a wave field of a fundamental shear horizontal guided wave in a plate structure. The reflection coefficient of a guided wave from a rectangular discontinuity can be modeled in the same way as the total reflection coefficient of a bulk wave. For the discontinuity having a slightly changed cross-sectional area, the reflection coefficient from the whole discontinuity can be calculated by spatial integration of the waves reflected from the divided regions. Some experiments and analyses were performed for 4mm-thick stainless steel plate specimens with EDM notches using a 300kHz frequency shear horizontal angle beam sensor, and for a cylindrical shell specimen (4.2m inner diameter, 9mm wall thickness) with discontinuities using a 40kHz frequency shear horizontal inter-digital sensor. The experimental reflection amplitudes were in good agreement with the analytical reflection amplitudes derived by the proposed model.