In this study, effects of salt stress, SNP and plant hormones on acticities of antioxidant system in sunflower (Helianthus annuus L. cv. Tarsan-1018) leaf tissues were investigated. The study was conducted in 2016 under controlled climate room conditions. The seeds were irrigated with culture solution for 5 weeks. At the end of the fifth week, salt, SNP and hormone applications were applied for 48 hours. At the end of 48-hour samples were gathered. Superoxide dismutase activity, Catalase activity, Glutathione S transferase activity and Proline amount were determined according to Sairam et al. (2002), Aebi (1984), Habig et al. (1974) and Ninhiydrin method (Troll and Lindsley, 1955), respectively. Results showed that salt stress and Sodium nitroprusside stimulated antioxidant defense. Plant hormones had different effects. Abscisic acid had positive effects on antioxidant defense. Gibberellic acid caused negative effects on enzyme activities and proline amount.