Through adjusting the position of the closure gap of Caofeidian southeast seawall cofferdam and adopting the layered construction method, we improved the safety of closure construction. Applying the doublelayer geotextile cushion method, we enhanced the seawall’s stability against sliding. The closure construction was implemented successfully under the condition of 2.37 m fall head, 4 m/s average speed of cross-flow and 6 m/s maximum instantaneous flow speed, and the construction cost was cut down.