Abstract: A pot experiment was carried out to test the effects of salt levels on root morphology as well as the relationship between root morphology and salt tolerance with four cotton cultivars (salt-sensitive cultivar CCRI45, weak salt-resistance cultivar XLZ17, moderate salt-resistance cultivar XLZ13 and salt-resistance cultivar CCRI35). Results showed that dry mass and K⁺/Na⁺ ratio of cotton root and leaf were significantly reduced by salt stress. Dry mass of root and leaf and K⁺/Na⁺ ratio of root of cultivars XLZ13 and CCRI35 were 69.3%-104.4%, 24.8%-45.3% and 25.0%-45.8% higher than those of cultivar CCRI45, respectively. Root development was significantly restrained by salt stress. Total root length, total root surface area and total root volume of cultivars XLZ13 and CCRI35 were 15.2%-85.8%, 12.0%-68.5% and 31.7%-217.8% higher than those of cultivar CCRI45, respectively. Furthermore, the length of fine and middle roots, root surface area and root volume of cultivars XLZ13 and CCRI35 in 0-10 cm soil layer were 27.2%-73.9%, 39.6%-74.3% and 99.0%-309.7% higher than those of cultivar CCRI45, respectively. Results from principal component analysis showed that the variations of specific root length, root length ratio at 0-10 cm soil layer and fine root length ratio at 0-10 cm soil layer among cultivars was significant. Specific root length, root length ratio at 0-10 cm soil layer and fine root length ratio at 0-10 cm soil layer were the main root characters to distinguish different salt tolerant cotton cultivars. Results from the stepwise regression analysis showed that specific root length, coarse root length, coarse root area, and coarse root volume at 0-10 cm and 10-20 cm soil layers, as well as fine root area and middle root ratio at 0-10 cm soil layer were sensitive to salt. Salt tolerant cultivar adapted to salt stress through increasing root length ratio, fine length ratio, and specific root length.