This paper presents a grasp planning method that takes into account center of gravity of objects in a pre-computation phase, thereby improving an existing method for grasp planning in complex scenes[1]. In the pre-computation phase, the system additionally calculates the distance from fingertips to the center of gravity of an object to use in ranking different proposed grasps, in order to achieve stable grasping with less force. Then we implement the proposed system in the OpenRAVE[2] environment that provides the original method[1]. Evaluation experiments were conducted with the Kawada Nextage[3] robot fitted with our original hand. Results show that the proposed method always grasps target objects closer to their center of gravity.