Abstract: Six melon varieties (Jiuhongrui, 2-64, Jiuqingmi, 002, Jiucuimi, Jiuxian), falling into three cultivars, were used as test materials in order to study the effects of sustained sub-low temperature in night(8~15 ℃）and normal in daytime on the physiological and biochemical indexes at seedings stage. The results showed that: during the sustained sub-low temperature treatments, the changes of soluble protein content increase in the beginning and decrease in the later in all varieties. the soluble protein content of Jiuqingmi decrease in the first and increase in the later, others decrease all the time.The change of electrolytic leakage is , the electrolytic leakage of Jiuqingmi and 2-64 decreases, others’ increase. The proline content of Jiuqingmi, Jiuhongrui and Jiuxian decrease first and increase later,others’ decrease all the time. the changes of proline content in Jiuqingmi、002 and Jiuxian decrease in the first and increase in the later, Jiuhongrui and 2-64 decrease all the time, Jiucuimi increase in the first and decrease in the later. The authors kow from the comprehensive analysis , Jiuqingmi and Jiuhongrui have better tolerance of the sustained low temperature and can be used in production.