In high average power multi-pass amplifier systems, Pockels cell, used for isolating and controlling number of passes, encounters both limitation of aperture and thermo-effects. We propose and demonstrate for the first time, as far as we know, a reflecting Pockels cell (RPC) which is longitudinally excited based on KD*P utilizing matched a discharge chamber and a copper plate as electrodes. In the RPC, electro-optic crystal can be longitudinally conduction-cooled. This device, with a 40 mm x 40 mm clear aperture, can be scaled to larger, and driven by one low voltage pulse. Excellent switching efficiency, high static extinction ratio, and negligible thermo-effects have been achieved.