Abstract: With the materials of Salix hybrid seedlings, the effects of NaC1, Na2SO4, NaHCO3, Na2CO3 and complex alkali-saline stress on root activity were studied using completely random blocks design. The effects of sodium nitroprusside (SNP) and the exogenous nitric oxide donor on root activity of Salix hybrid seedlings under salt stress with the concentration of 100 mmol/L were studied too. The results showed that the Salix hybrid had certain stress capacity under NaCI and Na2SO4 stress, when the concentration increased, the root activity declined after rising. Root activity always declined under NaHCO3 and Na2CO3stress. Under complex alkali-saline stress, the root activity declined after rising with salt concentration increased, when pH value varied from 6. 89 to 7. 14. When the pH value was greater than 8.22, root activity declined with the concentration increased. Under single-sah stress, the SNP didn’ t play a mitigation role in NaC1 stress. Under Na2SO4, NaHCO3 and Na2CO3 stress, they all had a certain mitigation. Under complex alkali-saline stress, SNP’s mitigation capacity decreased gradually with the pH value increased.