Heavy metal pollution is harmful to the environment and to human health. Resistant strains can grow in adverse conditions and store heavy metals to reduce their damage. The Cd2+ resistant mutant strain C2, which was irradiated by the C-12(6+) beams, can grow in Cd medium ranging from 20 to 100 mg L-1 when compared with the original strain. Attempting to discern the cause of the resistance, the phenotype and antioxidant defense system were analyzed. SEM images showed that when exposed to Cd2+, gaps on the cell surface were filled with a complex granular compound. FT-IR demonstrated that the alcoholic hydroxyl group, amino, and amide groups combined with ions. Moreover, responses of antioxidant defense system were different in the Cd2+ groups. The expression of SOD peaked at 24 h in high concentrations of Cd2+; the content of GSH increased gradually and was significantly affected by cultivation time. The MDA and CAT had the strongest response to 20 mg L-1 Cd2+ and the related metabolic pathway of CAT might play a key role in the resistance to high concentrations of Cd2+, The result indicated that the applicability of C2 could provide potential biotechnology for treatment of waste-waters and soils with Cd pollutions.