Using Sophora alopecuroides and Thermopsis lanceolata as materials,under 25 ℃,the imbibed seeds were taken out as a sample every 24 h.The non-imbibing seeds after 10 d were regarded as hard seed (H).Imbibing seeds and hard seeds that imbibed for 24 h after treated with sulfuric acid were all subjected to germination test and several vigour tests.The results indicated that:(1)The numbers of the seeds newly imbibed in one day were gradually decreased along with time.The hard seeds of S.alopecuroides had a relative slow rate of imbibition,which was decreased below 1% after 10 d,while the imbibition rate of T.lanceolata was at the same level after 3 d,another decrease happened after a sudden increase in 9th to 10th day.(2)The germination rate,germination index,vigour index,the activity of dehydrogenase,respiration rate and SOD activity of hard seeds were significantly higher than those of non-hard seeds in both species,while the relative conductivity,the contents of soluble sugar and malondialdehyde of hard seeds were lower than those of non-hard seeds.Studies showed that the vigour of hard seeds were higher than that of imbibing seeds,and the vigour of imbibing seeds were increased gradually with the initial imbibing time postponed.