Abstract: The purpose of this study was to understand the drought tolerance of Cercis gigante seed in germination stage.The seeds were soaked at 80 ℃ hot water for 12h,then treated with 150 mg/L gibberellin for 12h,and finally stratified at low temperature for one month. After dormancy breaking,the seeds of Cercis gigante seeds were germinated on filter paper in Petri dish gauze under different concentration of PEG solution. Effects of drought stress on seed germination percentage, seedling growth, protective enzyme activity and organic osmoregulation substances were studied.A regression analysis was conducted between PEG concentration and the germination rate, radicle length and so on. Results showed that: ① Under PEG stress, the seed germination rate, germination index, vigor index, radicle and hypocotyl length showed a trend of rising first and then decline with the aggravating of drought stress,indicating that low concentration(5%)of PEG could promote the seeds germination and growth, whereas high concentrations(10%,20%, 30%)had the inhibition effects. ② With the increase of PEG concentration, contents of three kinds of organic regulation substances(soluble sugar, soluble protein and free proline)and SOD activity in Cercis gigante seedsall showed a trend of decline first and then rising.POD activity showed a trend of rising first and then decline.Thus it could be seen that the drought tolerance of Cercis gigante seeds could be improved by increasing protective enzyme activities and contents of osmotic regulation substances, making the inhibition degree to the minimum.