| 【Objective】The study was conducted to understand the influence of NaCl stress on seedling root morphology
of Tibetan highland barley at the bud stage and its relationship with salt tolerance, and to screen out salt-tolerant barley
varieties（lines）.【Method】With quartz sand as the substrate, the highland barley was treated with 0 mmol/L, 50 mmol/L,
100 mmol/L, 150 mmol/L, 200 mmol/L and 250 mmol/L NaCl solution, and NaCl stress of median lethal concentration（LC50）
was obtained by regression analysis with the relative vigor index（RVI）as an indicator. The LC50 of NaCl was used to treat 28
highland barley samples. The effects of NaCl stress on the morphological characteristics of highland barley roots were studied,
and salt-tolerant highland barley varieties（lines）were screened out.【Result】The RVI of Tibetan highland barley seedlings showed a decreasing trend with the increase of NaCl solution concentration. The regression equation of NaCl stress concentration
and RVI was: y=-0.0022x + 0.9107. With LC50 as the concentration stress, the germination rate, bud length, longest root length,
fresh weight per plant and dry weight per plant of highland barley seedlings at the bud stage were all affected to varying degrees.
Among them, bud length was the most sensitive and fresh weight per plant was the most insensitive. Correlation analysis showed
that the RVI was significantly correlated with the relative germination rate, extremely significantly correlated with the longest root
length, and extremely significantly positively correlated with the dry weight per plant. The cluster analysis results showed that,
at the third Euclidean distance, the highland barley could be divided into four types, of which the RVI of type A reached 0.71,
with the strongest salt tolerance.【Conclusion】The median lethal concentration of highland barley under NaCl stress is 186.68
mmol/L. The germination rate, root length and dry weight per plant can be used as auxiliary indicators for the selection of salttolerant materials for highland barley. Combined with the RVI and cluster analysis, 3 materials（WDM03018, WDM03722,
WDM04526）with strongest salt tolerance were screened out.