A floating seesaw shaped Wave Energy Converter (WEC) is proposed, composed of double pontoons and a vertical damping plate deep into water. The double pontoons are shaped in cylinder, and are rigidly connected. A damping plate is placed deeply underwater, connected with the double pontoons by a slender rod. Roll moment will be generated when ocean waves hit surface floated double pontoons, and a generator is placed to convert this roll moment into electricity. The motion model of the WEC is set up to estimate averaged power.