To discuss the influence of Cl^- for the growth and photosynthetic characteristics of sweet potato seedlings,the author used greenhouse hydroponics method to determine the physiology and biochemistry,and gas exchange data,which was taken by using exogenous chlorine stress (0,42.2,84.4,168.8,211 mmol·L^-1) to test on three samples (‘Xushu 22’,‘Sushu 11’ ,‘Ningzi 1’) for 7,14 and 21 days.The results showed that:(1)The growth rate of leaf area and vine length for sample ‘Xushu 22’ was depressed by using exogenous chlorine,but was able to maintain a certain level.On the contrary,the growth rate of leaf area and vine length for sample ‘Sushu 11’ and ‘Ningzi 1’ were able to maintain an increase in the same condition using the extra Cl^- (concentration of 84.4 mmol·L^-1).Under the use of 42.2 mmol·L^-1,the samples all show higher growth of net photosynthetic rate (P_n) and photosynthetic pigments content.(2)Non-stomatal limitation is the main cause for the decreasing of photosynthesis of sample ‘Xushu 22’.Sample ‘Sushu 11’ and ‘Ningzi 1’ show both non-stomatal limitation and stomatal limitation,which stomatal limitation is the more dominating when samples are under temporary or low concentrated exposure of Cl^-.(3)The Cl^- in the roots of sample seedlings for 21 d are less than for 14 d samples and the SCl from root to earth are higher;‘Xushu 22’ seedlings had lower Cl^- content than ‘Sushu 11’ and ‘Ningzi 1’.Conclusion:low concentration and short-term chlorine treatment benefits sweet potato growth and photosynthesis;At an early stage,the seedlings can effectively restrained the translocation of Cl^- to the aerial part,which is weakened after three weeks under the Cl^- treatment;Chloride stress tolerance showed genotypic variation in sweet potato and ‘Xushu 22’ exhibited higher tolerance.