Abstract: For knowing the reaction and adaptation of Ulmaceae species in karst areas to water stress and comparing their drought-resistant ability, the variation of physiological and biochemical indexes in seedlings of Pteroceltis tatarinowii, Celtis sinensis and Ulmus parvi f olia were studied by experiments of simulating water stress. The results showed the tendency of physiological and biochemical indexes in three seedlings under water stress were similar. The relative water deficit(RWD), plasma membrance permeability, proline content and injured degree of membrance raised as increasing of water stress level, and the xylem water potential (～w) decreased. The content of MDA raised first, declined then, and increased continually later, but the variation level of indexes in three seedlings were different. By coordinate composite evaluation,the results indicated that the drought-resistance ability of Ulmus parvifolia seedlings were first, the Pteroceltis tatarinowii seedlings were second, and the Celtis sinensis seedlings were inferior.