Abstract: Reaumuria soongorica from four geographical populations (Lanzhou Jiuzhoutai: LZJ, Wuwei Minqin: WWM, Zhangye Linze: ZYL and Jiuquan Jinta: JQJ) were studied in a natural environment. Eighteen physiological indexes of R. soongorica, including photosynthetic rate (Pn), transpiration rate (Tr), water use efficiency (WUE), chlorophyll, soluble sugar (SS), proline (Pro), malondialdehyde (MDA), superoxide dismutase (SOD), peroxidase (POD) were measured. Subordinate function and grey correlative analysis of drought-resistance and its relationship with drought-resistance indexes of R. soongorica were used for a quantitative evaluation of comprehensive drought resistance. The drought resistance capability of R. soongorica from four geographical populations was in the order WWM＞JQJ＞ZYL＞LZJ. There was a general tendency in lower water conditions for more capable drought resistance with the result that plants adapted to environmental condition through adjusting their physiology. Eighteen drought resistant indexes were restricted and relied on each other in the drought resistance mechanisms of the plant, and they adjusted the inner drought resistance mechanisms comprehensively. The three main mechanisms (increasing WUE through declining Tr, the xanthophyl cycle-dependent thermal energy dissipation, and osmoregulation mechanisms) mainly rely on Pro and occupy an important place in the drought resistance mechanisms of R. soongorica.