Abstract: In order to improve the estimation accuracy of freeboard of Antarctic sea ice, this paper combined CryoSat-2 altimeter data, ASPeCt ship observational data and IceBridge airborne altimeter data to explore the optimal parameters for freeboard estimation using the minimum method, as well as analyzed spatiotemporal variation of sea ice freeboard from May to October, 2011-2017 in the Weddell sea. The result indicates that the optimal parameter scheme for retrieving freeboard is to apply the average of the lowest 5% measurements as local sea surface height after eliminating the gross data using 0.8 times standard deviation within 10 km segment. Over the past seven years, sea ice freeboard in the Weddell sea presents a slightly thinning trend, and monthly average freeboard ranges from 17.9 cm to 27.4 cm. The distribution of sea ice freeboard of the Weddell sea is characterized by the thick sea ice located in the west Weddell sea and near the Antarctic Peninsula, while thin sea ice distributed in the east Weddell sea. This study could be beneficial for further studying the response of the Antarctic sea ice thickness to climate change.