A study of the response of sugar content,enzyme activities of sugar metabolism and photosynthetic parameters in leaf of Lycium barbarum under water stress aimed at providing theoretical basis for high-yield planting of this plant in the arid regions.The results showed that:(1)The sucrose and starch contents in leaves were reduced under water stress at the green fruit stage,but their contents increased under light drought at the color fruit stage.The starch content in leaves gradually increased with drought aggravated.(2)The activities of neutral invertase(NI),sucrose phosphate synthase (SPS) and sucrose synthase (SS) in leaves were gradually reduced under drought stress at the green fruit stage.The activities of acid invertase (AI) and SS were reduced at the color fruit and maturing stages,but the activities of NI was increased at these two stages.(3)With the increasing of drought stress,the leaf net photosynthetic rate (P_n),transpiration rate (T_r) and stomatal conductance (G_s) were gradually lowering.The water use efficiency (WUE) was light drought (LD)＞normal irrigation (CK)＞severe drought (SD)＞moderate drought (MD).It is therefore suggested that light drought can promote the sucrose content and WUE in leaf and transport more photoassimilates to the fruit.