To explore the responses to salt stress in germinating stage and seedling stage of Silybum marianum (L.) Gaertn.(white rind type,HW;black rind type,SD),and compare the salt tolerances of two S.marianum cultivars.Treating the seeds and seedlings of two S.marianum cultivars by different concentrations of NaCl,germination energy,germination rate,bud seedling,seedling growth condition and physiological and biochemical characteristics were observed.Results showed that:(1)The germination energy,germination rate decreased under NaCl stress.The low density NaCl showed promting function and high density NaCl expressed inhibitory function(HW:NaCl concentration≥0.5%,SD:NaCl concentration≥0.3%) on the bud seedling growth.NaCl has great influence on radical,plumular axis length and fresh weight,and has no significant effect on dry weight.(2)The content of malondialdehyde (MDA) increased in young leaves,while photosynthetic pigment contents decreased.The low density NaCl showed promting function and high density NaCl expressed inhibitory function(HW:NaCl concentration≥0.9%,SD:NaCl concentration≥0.7%) on the seedling growth.The soluble sugar,soluble protein contents and activities of protective enzymes (including SOD,POD and CAT) increased at first and then decreased in young leaves,among them,soluble sugar and protein contents decreased significantly than that of control when NaCl concentration was 0.9%,while the activities of protective enzymes decreased significantly than that of control when NaCl concentration was 0.7%.Proline content increased continuously.It was found that NaCl effected bud seedling growth by altering the ability of seed imbibition at the seed germination stage,and S.marianum seedlings could promote the osmotic substance contents and activities of protective enzymes to relieve the damage of NaCl at seedling stage.The ability of salt tolerance at seedling stage was significantly stronger than that at germinating stage of S.marianum,and the ability of salt tolerance of HW was stronger than that of SD.