Abstract: Taking willow clones SH31 as trial material, the distribution and changes of photosynthetic characteristics of Na+, K+, Ca2+ in roots, stems and leaves were studied in the condition of hemi-inhibitory sodium chloride solution. The results are as follows: under the stress of 0.6% sodium chloride solution, willow clones SH31 appeared strong salt tolerance. In the condition of hemi-inhibitory sodium chloride solution, concentration of Na+ increased in roots during the first 16 days and part of Na+ was intercepted to transport to the leaves. In the condition of hemi-inhibitory sodium chloride solution, the content of K+ decreased in roots and stems, however it increased in leaves. It can still maintain high level K+ in leaves. There was no significant difference of content of Ca2+ in roots, stems and leaves between treatment and control. In this condition, the net photosynthetic rate of SH31 reduced during the first 7 days and then remained stable. The transpiration rate and stomatal conductance decreased during the first 7 days and then increased. However, there was no significant difference of the concentration of CO2 between treatment and control. The root selective absorption of Na+ and maintaining large amount of K+, Ca2+ and high level of photosynthesis should be the important mechanism of salt tolerance in SH31.