The effects of freezing stress on the protein expression profile and enzyme activity change in Antarctic green microalga were examined in this investigation. Antarctic green microalga was cultured at $4^{circ}C$ for optimal growth, and the temperature was reduced near to $0^{circ}C$ in order to apply freezing stress. The resultant differentially expressed proteins induced by freezing stress were analyzed by mass spectrometry following two-dimensional gel electrophoresis (2-DE). In total, about 320 protein spots were detected on the 2-DE gel, and 17 proteins showed a greater than two-fold change in abundance; of these, 5 proteins were up-regulated, and 12 proteins were down-regulated. Moreover, total enzyme activities and isozyme patterns of several antioxidant enzymes, named catalase, superoxide dismutase and aldehyde dehydrogenase were changed upon applying freezing stress.