In order to study the salicylic acid (SA) on the growth of cotton seedlings under salt stress and resistance physiology, We used ‘ Zhongmiansuo 41’ (tolerant varieties) and ‘Zhongmiansuo 49’ (medium tolerant varieties) as material. On 0.60% NaCl stress conditions, using seed soaking and spraying application method of exogenous SA cotton, we investigated the seedling growth, osmotic adjustment matter content and antioxidant system. The results showed that: (1) NaCl stress significantly inhibited the growth of cotton seedlings, under NaCl stress with SA soaking+spraying treatment, cotton seedling height, leaf area, dry mass, root activity, root/shoot ratio were increased, and malondialdehyde (MDA), soluble sugar (SS), soluble protein (SP) and proline (Pro) contents were increased in leaves when exogenous SA had been applied, together with significant decrease in superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities in leaves and roots. The activities of SOD, POD and CAT in roots of cotton seedlings were smaller than those of leaves, and the SA treatment increased the enzyme activities of cotton seedling roots more than that in leaves; (2) SA soaking+spraying composite treatment on 0.60%NaCl mitigation effect is better than that of SA seed soaking treatment, while the 0.05 mmol·L^-1 soaking +0.2 mmol·L^-1 spraying treatment is the best; (3) Comparison of two varieties, SA on the ‘Zhongmiansuo 49’ to alleviate salt stress intensity is greater than that on the ‘Zhongmiansuo 41’, especially in cotton seedling root growth is most evident, exogenous SA could made the root activity of ‘Zhongmiansuo 41’ improved 10.58%-57.56%, ‘Zhongmiansuo 49’ improved 15.08%-80.48%. The study found that exogenous SA could alleviate cell membrane damage and increase salt tolerance by regulating osmotic adjustment and antioxidant capacity of cotton seedlings, but the effect of alleviation was different between different tolerant cultivars and treatments.