The change of water parameters (Ψsats, Ψtlps, ROWCtlp, RWCtlp,AWC,Va/V0 and εmax ) in Tetraena mongolica with season and habitat was studied by means of press-volume technique. The results showed as follows：(1) Tetraena mongolica is of low Ψsats, low Ψtlps, high AWC and high Va/V0, which shows that Tetraena mongolica is of strong ability of drought tolerance. (2) The seasonal change of Ψsats,Ψtlps and εmax showed May＞July＞September. And the AWC,Va/V0 showed May＜July＜September. The drought tolerance of Tetraena mongolica continuously enhanced with season. This seasonal change is response to the phonological rhythm of plant. (3) The ordination analysis for drought tolerance of Tetraena mongolica in upland, hill,tableland, high plain, terrace was finished. The level of drought-tolerance among the five habitats above decreased in the following order: high plain and terrace＞upland＞tableland＞hill. Based on three measurements of water parameters of Tetraena mongolica in five habitats in P-V curves, the cluster analysis of drought tolerance of Tetraena mongolica was finished. Tetraena mongolica in five habitats can be classified into two groups: upland, hill and tableland is one group, high plain and terrace is the other group. The variance analysis showed that three measurements of Ψsats,Ψtlps and AWC of Tetraena mongolica in high plain and terrace is lower than that of upland, hill and tableland. There are difference in osmotic adjustment mechanism among five different habitats. Tetraena mongolica in high plain and terrace is of stronger ability of osmosis adjustment by improving the concentration of cellular solute, but Tetraena mongolica in upland, hill and tableland is of stronger ability of holding water (high AWC).