In the general process, GPS is used for the positioning in the airborne lidar operation. Therefore, most frequently the height obtained is referenced to WGS84 ellipsoid and the measurements are in ellipsoidal height. In order to produce the digital elevation model in the orthometric height, the geoid undulation correction should be performed. This paper investigates the differences of five currently available digital geoid models of Taiwan area as applied to the airborne lidar point cloud obtained for the Kao-Hsiung and Ping-Tung area. Based on the differences between the result from the elevation obtained in the field and the elevation interpolated from the Lidar point clouds, the ellipsoid height are examined. The standard deviation for the ellipsoid heights is 0.172m. Then, the orthometric height differences among those obtained from different models are compared. The standard deviation for Hwang-2005 is 0.174m, and 0.199m for Hwang-2001. Due to the lack of directly observed orthometric heights, the real error in terms of orthometric height is still difficult to confirm.