Calmodulin (CaM) is a Ca2+-binding protein that plays a role in several Ca2+ signaling pathways, which dynamically regulates the activities of hundreds of proteins. The ice alga Chlamydomonas sp. ICE-L, which has the ability to adapt to extreme polar conditions, is a crucial primary producer in Antarctic ecosystem. This study hypothesized that Cam helps the ICE-L to adapt to the fluctuating conditions in the polar environment. It first verified the overall length of Cam, through RT-PCR and RACE-PCR, based on partial Cam transcriptome library of ICE-L. Then, the nucleotide and predicted amino acid sequences were, respectively, analyzed by various bioinformatics approaches to gain more insights into the computed physicochemical properties of the CaM. Potential involvements of Cam in responding to certain stimuli (i.e., UVB radiation, high salinity, and temperature) were investigated by differential expression, measuring its transcription levels by means of quantitative RT-PCR. Results showed that CaM was indeed inducible and regulated by high UVB radiation, high salinity, and nonoptimal temperature conditions. Different conditions had different expression tendencies, which provided an important basis for investigating the adaptation mechanism of Cam in ICE-L.