Abstract: Changes in both the area and thickness of Arctic sea iceare significantly influenced by global climate change the rapid decline in Arctic sea ice during the summer of 2007 is analyzed empirically in our research. Sea ice thickness can be retrieved from the sea ice freeboard heights. As ICESat/GLAS (ice, cloud and land elevation satellite/geoscience laser altimeter system) provide high-precision sea ice elevation information, therefore we could extract the freeboard heights of the Arctic sea ice from ICESat/GLAS datasets spanning from 2003 to 2008 to analyze seasonal and inter-annual variation in Arctic sea ice. The results show that the Arctic sea ice freeboard heights have been decreasing during 2003-2008, especially in the summer of 2007. Systematic deviationsin the retrieved results are discussed and analyzed based on the ULS (Upward Looking Sonar) field data.