Sea ice concentration (SIC) is an important parameter in characterizing sea ice. Limited by the environment and the spatial extent of observation, it is difficult for field work to meet the needs of a large-scale SIC study. However, with its many advantages, such as the ability to make large-scale, high-resolution and long-duration observations, the altimeter can be used to determine SIC on a large scale. Using the correspondence between the satellite pulse altimeter waveform and reflector property, waveform classification is employed. Moreover, this paper develops an algorithm to obtain the SIC from altimeter waveforms. In an actual computation, Pyrz Bay in the Antarctic is taken as an experimental region, and one-year and seasonal SICs are derived from ERS-1/GM waveforms over this study area. Furthermore, altimetric SICs are compared with those of SSMR SSM/I. The results show that the spatial distribution and the regions of maximum SIC determined employing these two methods are consistent. This demonstrates that altimeter data can be used to monitor sea ice. Limited by the environment and the spatial extent of observation, it is difficult for field work to meet the needs of a large-scale SIC study. However, with its many advantages , such as the ability to make large-scale, high-resolution and long-duration observations, the altimeter can be used to determine SIC on a large scale. Using the correspondence between the satellite pulse altimeter waveform and reflector property, waveform classification is employed Moreover, this paper develops an algorithm to obtain the SIC from altimeter waveforms. In an actual computation, Pyrz Bay in the Antarctic is taken as an experimental region, and one-year and seasonal SICs are derived from ERS-1 / GM waveforms over this study area that SSID SSM / I. The results show that the spatial distribution and the regions of maximum SIC determined employing these two methods are consi stent. This demonstrates that altimeter data can be used to monitor sea ice.