To determine the germination and morphological response of Yellow Horn (Xanthoceras sorbifolia) to soil moisture and drought stress,seed germination and seedling growth of Yellow Horn were assessed under controlled conditions that simulated drought stress induced by polyethylene glycol (PEG-6000) in seed germination box.Water stress was supplied through incubation in seven different concentrations (5%,10%,15%,20%,25%,30% and 35%) of PEG-6000 that provide solutions with water potentials being separately -0.58,-1.66,-3.25,-5.34,-7.94,-11.05 and -14.66 MPa.The experiment was designed as a completely randomized design with one factor.The results showed that:(1)The germination capacity,planting percent,root length and relative permeability of cell membrane decreased with a decrease in osmotic potential,whereas free proline content,MDA content and the number of roots of seedling increased.(2)The seed germination,planting percent and the number of roots in 5% of PEG concentration was higher than that of control treatment,and mortality was lower.At the same time,seedling height in 5%~10% of PEG concentreation was higher than that of control treatment,but did not differ significantly from control.(3)More dramatic differences between PEG concentration were evident when the effects of water stress on seed germination,planting percent,mortality,root length,the number of roots and free proline content,MDA content and relative permeability of cell membrane were evaluated.These findings form the rang of water potential which Yellow Horn can suffer from was -7.94~-11.05 MPa.