Spars are floating complaint structures used for deepwater oil explorations. The heave motion response of spar is very important for the selection of suitable drilling and production equipments. Spar platform can possibly be subjected to heave resonant oscillations during the swell conditions. To reduce the heave motions one of the most effective methods is to use damping devices in the form heave plate which is attached to the keel of the spar. This will reduce the heave response in two ways; by increasing the added mass of the spar and by increasing the viscous damping by vortex shedding process. In the present study the influence of damping plates on the heave response of the spar is studied using WAMIT software. The configurations of the heave plates taken into considerations include single circular heave plate with different diameter configuration and twin circular heave plates with different spacing configurations. The effect of disc diameter and spacing on the heave added mass is studied. The diameter ratio defined as the ratio of the diameter of the heave plate to the diameter of the spar (Dd/Ds) considered for study are in the range of 1.1 to 1.4 and it is observed that as the plate diameter increases the reduction in the heave response also increases. Based on the study a plate diameter which is 20% to 30% more than the spar diameter found to be effective in heave motion reduction. For different spacing configurations, spacing ratio (L/Dd) 0.1 to 0.4 is considered. It is observed that as the spacing ratio increases the heave motion of the spar reduces. A spacing ratio in the rage of 0.2 to 0.4 is found to be effective in heave motion reduction. It is also inferred from the study that the effect of the heave plates on the pitch and surge motions is minimal (no effect). Copyright 2014, Offshore Technology Conference.