Salicornia persica is a family of spinach species (Chenopodiaceae) and halophiles , that has the ability to grow in saline soils. Because of this, it does not require fertile lands, that is economically viable for its cultivation. Due to its medicinal properties, it is also used in traditional medicine for treating diseases such as bronchitis, turmeric, diarrhea, lowering blood glucose level, anti-inflammation and cytotoxic activity. In other hand, no information is available on its antioxidant activity. this study was the first investigate on the antioxidant activity of this plant. In the present study, the antioxidant activity of the ethanolic extract of Salicornia persica plant was investigated using five model systems include, DPPH, reduce power, thiocyanate, radical hydroxyl and ?-carotene bleaching assay. Also, measure of peroxide and thiobarbituric acid index in sunflower oil was investigated and the activity of the extract of the plant was compared with the antioxidants BHT and ascorbic acid. The phenolic compounds in the extract of the plant were determined by spectrophotometry, using Folin-ciocalteu reagent, also total phenolic compounds and flavonoids were reported based on gallic acid and epicatechin, respectively. In the DPPH system and reduce power, the antioxidant activity of the plant extract was lower that of ascorbic acid, but compared to BHT, the extract of the plant showed more antioxidant activity. Thiocyanate system showed higher antioxidant activity than extract of BHT, but this difference, was not statistically significant (p 0.01), and ascorbic acid in this model had the least antioxidant activity. In radical hydroxyl system model, antioxidant activity of BHT was higher than plant extract and ascorbic acid, in the plant extracts and ascorbic acid were not significantly different (p 0.01). The Beta-carotene bleaching of the antioxidant activity was different in comparison to the ascorbic acid. In the third part of this study, the effect of ethanolic extract of Salicornia persica on delayed oxidation of sunflower oil was evaluated by measuring the peroxide and thiobarbituric acid index and compared with synthetic antioxidant BHT. For this purpose, the extract of Salicornia persica plant was added to sunflower oil at three levels of concentration (100, 300, 500 ppm) and BHT (100 and 200 ppm), than samples Samples were placed at 60 °C for 15 days. The results showed that different concentrations of the extract significantly (p 0.05) were able to reduce the oxidation process compared to the control sample. The lowest amount of peroxide and thiobarbituric acid in all days belonged to the concentration of 500 ppm of plant extract, which was better than 200 ppm BHT. Keywords: Salicornia plant, Antioxidant activity, phenolic compound