Abstract: The seasonal and interspecific changes of drought resistance index were studied in three tree species, Malus micromalus, Robinia pseudoacacia and Caragana korshinskii, based on the data of main water parameters measured by using pressure volume(PV) technique.The result showed that the seasonal change trend of drought resistance in the three species was closely related with both the growth and development stages and the environmental water conditions from May to October, and that the droght resistance in every species was the weakest in May, much stronger in June and July, weak at the autumn rapid growth stage and the strongest or every strong in October.Of these species the drought resistance had following order from strong to weak:M.micromalus,C.korshinskii, R.pseudoacacia.With its strongest drought resistance M.micromalus was a valuable fruit tree species in the triangle area of Shanxi, Shaanxi and Nei Monggol, Because of its great adaptive capacity to water stress C.korshinskii was of great value in both soil and water conservation and fodder production.

Key words: Pressure volume analysis, Drought resistance index, Malus micromalus, Robinia pseudoacacia, Caragana korshinskii