In the present paper, effect of heave plate on heave response of spar is investigated for spar with single and two heave plates. Free decay test is conducted experimentally on 1: 50 scale model of spar without heave plate and spar with single heave plate for finding the heave natural period and heave total damping. Free decay test is also carried out numerically using STAR-CCM+ and numerical results are compared with the experimental results. Heave response is investigated using ANSYS-AQWA software. Heave plate increases the added mass and damping. So the heave response is less for spar with heave plate. Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE).