Abstract: 3 different phenotypes of Cinnamomum camphora taken as test materials, the photosynthetic pigment content, superoxide dismutase (SOD) activity, peroxidase (POD) activity, catalase (CAT) activity, soluble sugar content, changes in the content of soluble protein, free proline content and malondialdehyde (MDA) content in the natural overwintering were measured in order to select cold resistant strong C.camphora varieties. The results showed that the photosynthetic pigment content was stable in the early stage, but began to slow down in the later period. The content of soluble sugar increased rapidly in the early stage, then decreased slowly, and increased first in the late stage, then decreased. The content of soluble protein increased rapidly in the early stage after the rapid decline, and maintains a relatively low level. The free proline content decreased after a small rise in early stage, but increased rapidly in the late stage. SOD activity and CAT activity increased rapidly in the early stage, then decreased rapidly, and keep in a low level. The activity of POD decreased in the early stage after the rise, but the rapid rise in the late stage. The content of MDA in the early decline, and maintain a relatively low level, restored to the original level later and quickly with the change of temperature in the natural overwintering process. Free proline and POD are closely related in the cold resistance of camphor in the late natural overwintering process. The photosynthetic pigment content, SOD activity, POD activity, CAT activity, the soluble sugar content, soluble protein content and free proline content of phenotype 1 were significantly higher than those of 2 and 3, and the MDA content was significantly lower than that of the 2 and 3. With the comprehensive evaluation results of membership function method, the cold resistance of C.camphora in natural overwintering divided into enhancement phase, the strongest enhancement period, weakening stage and another enhanced period in the process of decreasing, phenotype 1 has the strongest cold resistance, can be used as cold resistant varieties in North jiangsu.