In order to explore the effects of combined application controlled-release urea and humic acid on the growth and the antioxidant system of cotton seedlings under salt stress. A pot experiment was conducted with coastal saline soil (4.5 g/kg of total salt) under five treatments, including no nitrogen fertilizer (CK), common urea (U), controlled-release urea (CRU), common urea + humic acid (U+HA) and controlled-release urea + humic acid treatments (CRU+HA). Cotton biomass, chlorophyll content, antioxidant enzymes (SOD, POD, CAT) activity and peroxide (MDA, SO₂^·-) content in cotton leaves and roots were measured. The results showed that under salt stress, compared with the other treatments, CRU+HA treatment promoted the biomass of cotton seedlings, among of which, the above ground fresh and dry weights increased significantly by 13.46%-69.46% and 12.64%-82.23%, respectively (P<0.05). Chlorophyll a content in cotton leaves increased by 11.84% under CRU+HA treatment, Significantly higher than the CRU treatment. Compared with U and CRU treatments, U+HA and CRU+HA treatments promoted the activities of antioxidant enzymes in cotton leaves and roots, among of which, SOD, POD and CAT activities increased by 3.41%-42.84%, 4.376%-37.87% and 5.53%-64.61%, respectively. The activities of SOD, POD and CAT of CRU+HA treatment were significantly higher than those of the other treatments. In conclusion, under salt stress, CRU+HA improved the salt tolerance of cotton, mainly by increasing the chlorophyll content and antioxidant enzyme activity of leaves and roots.