To detect the effect of drought on one-year-old Lycium ruthenicum seedlings,we investigated the photosynthetic pigments,photosynthetic characteristics and chlorophyll fluorescence characteristics on four different soil contents:CK(21.18%-22.32% soil moiture),light stress(12.20%-13.82%),moderate stress(12.20%-13.82%) and severe stress(7.89%-8.73%).The results showed that:(1)the chlorophyll content and carotenoid content decreased with the decreasing soil water content.(2)Under the moderate stress,the net photosynthetic rate (P_n),the transpiration rate (T_r),stomatal conductance (G_s) decreased significantly.With the decreasing of soil water content,intercellular CO₂ concentration (C_i),the water use efficiency (WUE) increased,whereas stomatal limitation (L_s) performed the inverse trend.(3)With the increasing of the minimal fluorescence (F₀) and nonphotochemical quenching (q_n) value,the maximal fluorescence (F_m),maximal photochemical efficiency (F_v/F_m),actual photochemical efficiency (Ф_PSⅡ),and photochemical quenching (q_P) decreased.It indicated that the excess energy of the leaves of L.ruthenicum is dissipated by heat,and the open degree of the reaction center is reduced to avoid the damage of the PSⅡ reaction center.It suggested that L.ruthenicum keep on vigor above the limitation of 7.89% soil moisture,and the largest WUE and the higher P_n arrive on 12.20%-13.82% soil moisture.