The drought resistance of Nitraria tangutorum from four geographical populations,i.e.,Jiuzhoutai District of Lanzhou City( LZJ),Minqin County of Wuwei City(WWM),Linze County of Zhangye City(ZYL) and Jinta County of Jiuquan City(JQJ),are investigated regarding physiological and biochemical indices,including net photosynthetic rate,chlorophyll,soluble sugar,proline,malondialdehyde,superoxide dismutase and peroxidase.Using the methods of subordination function,grey correlation analysis and principal component analysis,the relationship of drought resistance with the indexes were evaluated systematically.The results show that the drought resistance of Nitraria tangutorum from four geographical populations was in order as JQJ> WWM> ZYL> LZJ,indicating a increasing trend of drought resistance with increasingly adverse circumstances.T his implies that the plant adapted to environmental conditions through adjusting its physiological features.T he seventeen drought resistant indices were restricted by and relied on each other in comprehensively conditioning drought resistance of Nitraria tangutorum.However,the main two mechanisms,i.e.,the xanthophyll cycle-dependent thermal energy dissipation and the photoprotective mechanism of photoinhibition,played the leading roles in the drought resistant mechanisms of Nitraria tangutorum.