Antarctic sea ice is a crucial component of the polar climate system, with profound implications for global climate. Sea ice thickness, as one of the key properties of sea ice, holds significant importance for understanding and predicting the influences of climate change by revealing its spatial and temporal distribution patterns and variation trends. However, current monitoring of Antarctic sea ice thickness is constrained by limited ground observations with restricted spatial and temporal coverage or short-term satellite observations, long-term sea ice thickness data remains elusive. To address this issue, this study utilized the continuous satellite radar altimetry data from Envisat and CryoSat-2 and constructed a consistent dataset of radar freeboard of Antarctic sea ice. Then, the penetration depth of radar signals through the snow covers over Antarctic sea ice was quantitatively estimated, and a method applicable to various sea ice-snow scenarios for estimating Antarctic sea ice thickness was developed. The estimated sea ice thickness shows an average absolute bias of approximately 0.28 m compared to in situ measurements from the Australian Antarctic Data Centre, and an average absolute bias of approximately 0.65 m compared to ICESat laser altimeter with a high correlation coefficient of 0.71. Analysis of the spatiotemporal variations of Antarctic sea ice thickness from 2002 to 2023 reveals that thick ice is predominantly concentrated in the western Weddell Sea and Bellingshuan/Amundsen Seas, while ice in other sea sectors is relatively thin. Antarctic sea ice thickness exhibited a slight decreasing trend before 2011, followed by an accelerated decline after 2011 (−0.03 m/a). The distribution and trends of Antarctic sea ice thickness exhibit distinct seasonal and regional characteristics.