Abstract: The effects of naphthalene acetic acid(NAA)on the cold tolerance of Caryota obtusa seedlings were conducted by several physiological indexes， The leaves of C. obtusa were sprayed with 0， 25， 50 and 100 mg·L-1 NAA solutions， the activities of superoxide dismutase (SOD)， peroxidase (POD)， and the contents of malondialdehyde (MDA)， proline， soluble protein and chlorophyll of C. obtusa were determined under 25℃， 5℃ and 25℃. It was indicated that all the above physiological indexes varied with different concentrations of NAA. Subordinate function values for different concentrations of NAA at 25℃ were 039，030，039 and 051， respectively. It was concluded that leaves sprayed with different concentrations of NAA could affect the cold tolerance of C.obtusa seedlings and the optimal concentration was 100 mg·L-1.

Key words: NAA, Caryota obtusa seedling, physiological index, cold tolerance