A double sodium layer (DSL) structure was observed during the night of June 13, 2000 over Wuhan, China (31¿N, 114¿E) by our Na lidar. The unique feature of this DSL is that a normal sodium layer at altitudes of 80 ~ 105 km was accompanied by a secondary sodium layer at altitudes of 105 ~ 125 km for about 2 hours. The lidar observation result together with that obtained from the nearby ionosonde and geomagnetic equipments are presented. While the exact mechanism responsible for this DSL formation is still unclear, some possible explanations and corresponding observation evidences are discussed.