The experiment was conducted with Alhagi sparsifolia of the natural vegetation area in fllower reaches of Tarim River to investigate the change of the chlorophyll fluorescence parameters such as actual photochemical efficiency of PSⅡ(Φ_PSⅡ),electron transport rate(ETR) and photochemical quenching index(q_P) and leaf water potential under 2 times/year,1 times/year irrigation regimes(0.42 m³/m² of every time) and no irrigation(CK),and to discuss the impact of the different irrigation regimes on the chlorophyll fluorescence characteristics.The conclusions were as following:(1)With decreasing irrigation regimes,the leaf water potential of A.sparsifolia significantly decreased,and was the least under CK.(2)The q_P,Φ_PSⅡ,ETR,the maximal photochemical efficiencies of PSII(F_v/F_m),chlorophyll SPAD value and the light saturation point of A.sparsifolia were initially increased with the decreasing irrigation regimes and then it decreased.Whereas,the non-photochemical quenching(NPQ) and the yield for dissipation by down-regulation(Y_NPQ) of A.sparsifolia were also reduced first with decreasing irrigation regimes and then it improved.(3)A.sparsifolia under CK and 2 times/year irrigation regimes suffered inhibitory effect which declined its light utilization capability and photochemical reaction,However the heat dissipation ability was improved.As a result,excessive amount of irrigation(2 times/year,0.84 m³/m²) or no water supply(CK) could restrict the photochemical efficiency and photosynthetic activity of A.sparsifolia.The right time and the moderate water supply(supply water once in the spring,0.42 m³/m²) was more conducive to A.sparsifolia to adapt to drought stress and maintain normal growth photosynthesis.